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1Properties

2Applications

3Gemstone

4Occurrence

5Radiometric dating

6Similar minerals

7Gallery

8See also

9References

10Further reading

11External links

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Zircon

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From Wikipedia, the free encyclopedia

Zirconium silicate, a mineral belonging to the group of nesosilicates

This article is about the mineral and gemstone. For other uses, see Zircon (disambiguation).

ZirconA lustrous crystal of zircon perched on a tan matrix of calcite from the Gilgit District of PakistanGeneralCategoryNesosilicatesFormula(repeating unit)zirconium silicate (ZrSiO4)IMA symbolZrn[1]Strunz classification9.AD.30Crystal systemTetragonalCrystal classDitetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m)Space groupI41/amd (No. 141)Unit cella = 6.607(1), c = 5.982(1) [Å]; Z = 4IdentificationColorReddish brown, yellow, green, blue, gray, colorless; in thin section, colorless to pale brownCrystal habittabular to prismatic crystals, irregular grains, massiveTwinningOn {101}. Crystals shocked by meteorite impact show polysynthetic twins on {112}Cleavage{110} and {111}FractureConchoidal to unevenTenacityBrittleMohs scale hardness7.5LusterVitreous to adamantine; greasy when metamict.StreakWhiteDiaphaneityTransparent to opaqueSpecific gravity4.6–4.7Optical propertiesUniaxial (+)Refractive indexnω = 1.925–1.961 nε = 1.980–2.015, 1.75 when metamictBirefringenceδ = 0.047–0.055PleochroismWeakFusibilityclose to 2,550 °C depend on Hf,Th,U,H,etc... concentrations.SolubilityInsolubleOther characteristicsFluorescent and radioactive,May form pleochroic halos,Relief: highReferences[2][3][4][5][6]

Zircon (/ˈzɜːrkɒn, -kən/)[7][8][9] is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is ZrSiO4. An empirical formula showing some of the range of substitution in zircon is (Zr1–y, REEy)(SiO4)1–x(OH)4x–y. Zircon precipitates from silicate melts and has relatively high concentrations of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green.

The name derives from the Persian zargun, meaning "gold-hued".[10] This word is changed into "jargoon", a term applied to light-colored zircons. The English word "zircon" is derived from Zirkon, which is the German adaptation of this word.[11] Yellow, orange, and red zircon is also known as "hyacinth",[12] from the flower hyacinthus, whose name is of Ancient Greek origin.

Properties[edit]

Optical microscope photograph; the length of the crystal is about 250 µm

Zircon is common in the crust of Earth. It occurs as a common accessory mineral in igneous rocks (as primary crystallization products), in metamorphic rocks and as detrital grains in sedimentary rocks.[2] Large zircon crystals are rare. Their average size in granite rocks is about 0.1–0.3 mm (0.0039–0.0118 in), but they can also grow to sizes of several cm, especially in mafic pegmatites and carbonatites.[2] Zircon is fairly hard (with a Mohs hardness of 7.5) and chemically stable, and so is highly resistant to weathering. It also is resistant to heat, so that detrital zircon grains are sometimes preserved in igneous rocks formed from melted sediments.[13] Its resistance to weathering, together with its relatively high specific gravity (4.68), make it an important component of the heavy mineral fraction of sandstones.[5]

Because of their uranium[14] and thorium content, some zircons undergo metamictization. Connected to internal radiation damage, these processes partially disrupt the crystal structure and partly explain the highly variable properties of zircon. As zircon becomes more and more modified by internal radiation damage, the density decreases, the crystal structure is compromised, and the color changes.[15]

Zircon occurs in many colors, including reddish brown, yellow, green, blue, gray, and colorless.[2] The color of zircons can sometimes be changed by heat treatment. Common brown zircons can be transformed into colorless and blue zircons by heating to 800 to 1,000 °C (1,470 to 1,830 °F).[16] In geological settings, the development of pink, red, and purple zircon occurs after hundreds of millions of years, if the crystal has sufficient trace elements to produce color centers. Color in this red or pink series is annealed in geological conditions above temperatures of around 400 °C (752 °F).[17]

Structurally, zircon consists of parallel chains of alternating silica tetrahedra (silicon ions in fourfold coordination with oxygen ions) and zirconium ions, with the large zirconium ions in eightfold coordination with oxygen ions.[18]

Applications[edit]

Sand-sized grains of zircon

Zircon is mainly consumed as an opacifier, and has been known to be used in the decorative ceramics industry.[19] It is also the principal precursor not only to metallic zirconium, although this application is small, but also to all compounds of zirconium including zirconium dioxide (ZrO2), an important refractory oxide with a melting point of 2,717 °C (4,923 °F).[20]

Other applications include use in refractories and foundry casting and a growing array of specialty applications as zirconia and zirconium chemicals, including in nuclear fuel rods, catalytic fuel converters and in water and air purification systems.[21]

Zircon is one of the key minerals used by geologists for geochronology.[22]

Zircon is a part of the ZTR index to classify highly-weathered sediments.[23]

Gemstone[edit]

A pale blue zircon gemstone weighing 3.36 carats

Transparent zircon is a well-known form of semi-precious gemstone, favored for its high specific gravity (between 4.2 and 4.86) and adamantine luster. Because of its high refractive index (1.92) it has sometimes been used as a substitute for diamond, though it does not display quite the same play of color as a diamond. Zircon is one of the heaviest types of gemstone.[24] Its Mohs hardness is between that of quartz and topaz, at 7.5 on the 10 point scale, though below that of the similar manmade stone cubic zirconia (8-8.5). Zircons may sometimes lose their inherent color after long exposure to bright sunlight, which is unusual in a gemstone. It is immune to acid attack except by sulfuric acid and then only when ground into a fine powder.[25]

Most gem-grade zircons show a high degree of birefringence which, on stones cut with a table and pavilion cuts (i.e., nearly all cut stones), can be seen as the apparent doubling-up of the latter when viewed through the former, and this characteristic can be used to distinguish them from diamonds and cubic zirconias (CZ) as well as soda-lime glass, none of which show this characteristic. However, some zircons from Sri Lanka display only weak or no birefringence at all, and some other Sri Lanka stones may show clear birefringence in one place and little or none in another part of the same cut stone.[26] Other gemstones also display birefringence, so while the presence of this characteristic may help distinguish a given zircon from a diamond or a CZ, it will not help distinguish it from, for example, a topaz gemstone. The high specific gravity of zircon, however, can usually separate it from any other gem and is simple to test.

Also, birefringence depends on the cut of the stone in relation to its optical axis. If a zircon is cut with this axis perpendicular to its table, birefringence may be reduced to undetectable levels unless viewed with a jeweler's loupe or other magnifying optics. The highest grade zircons are cut to minimize birefringence.[27]

The value of a zircon gem depends largely on its color, clarity, and size. Prior to World War II, blue zircons (the most valuable color) were available from many gemstone suppliers in sizes between 15 and 25 carats; since then, stones even as large as 10 carats have become very scarce, especially in the most desirable color varieties.[27]

Synthetic zircons have been created in laboratories.[28] They are occasionally used in jewellery such as earrings. Zircons are sometimes imitated by spinel and synthetic sapphire, but are not difficult to distinguish from them with simple tools.

Occurrence[edit]

World production trend of zirconium mineral concentrates

Zircon is a common accessory to trace mineral constituent of all kinds of igneous rocks, but particularly granite and felsic igneous rocks. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a common constituent of most sands.[29][30] Zircon can occasionally be found as a trace mineral in ultrapotassic igneous rocks such as kimberlites, carbonatites, and lamprophyre, owing to the unusual magma genesis of these rocks.[citation needed]

Zircon forms economic concentrations within heavy mineral sands ore deposits, within certain pegmatites, and within some rare alkaline volcanic rocks, for example the Toongi Trachyte, Dubbo, New South Wales Australia[31] in association with the zirconium-hafnium minerals eudialyte and armstrongite.

Australia leads the world in zircon mining, producing 37% of the world total and accounting for 40% of world EDR (economic demonstrated resources) for the mineral.[32] South Africa is Africa's main producer, with 30% of world production, second after Australia.[33]

Radiometric dating[edit]

SEM-CL image of Zircon grain showing zonations and poly-cycles (core-rim structure)

Zircon has played an important role during the evolution of radiometric dating. Zircons contain trace amounts of uranium and thorium (from 10 ppm up to 1 wt%)[14] and can be dated using several modern analytical techniques. Because zircons can survive geologic processes like erosion, transport, even high-grade metamorphism, they contain a rich and varied record of geological processes. Currently, zircons are typically dated by uranium-lead (U-Pb), fission-track, and U+Th/He techniques. Imaging the cathodoluminescence emission from fast electrons can be used as a prescreening tool for high-resolution secondary-ion-mass spectrometry (SIMS) to image the zonation pattern and identify regions of interest for isotope analysis. This is done using an integrated cathodoluminescence and scanning electron microscope.[34] Zircons in sedimentary rock can identify the sediment source.[35]

Zircons from Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, have yielded U-Pb ages up to 4.404 billion years,[36] interpreted to be the age of crystallization, making them the oldest minerals so far dated on Earth. In addition, the oxygen isotopic compositions of some of these zircons have been interpreted to indicate that more than 4.3 billion years ago there was already liquid water on the surface of the Earth.[36][37][38][39] This interpretation is supported by additional trace element data,[40][41] but is also the subject of debate.[42][43][44] In 2015, "remains of biotic life" were found in 4.1-billion-year-old rocks in the Jack Hills of Western Australia.[45][46] According to one of the researchers, "If life arose relatively quickly on Earth ... then it could be common in the universe."[45]

Similar minerals[edit]

Hafnon (HfSiO4), xenotime (YPO4), béhierite, schiavinatoite ((Ta,Nb)BO4), thorite (ThSiO4), and coffinite (USiO4)[14] all share the same crystal structure (IVX IVY O4, IIIX VY O4 in the case of xenotime) as zircon.

Gallery[edit]

Crystal structure of zircon

Unit cell of zircon

Scanning electron microscope image of zircon

Unusual olive-green zircon

Cluster of three compound crystals of zircon

See also[edit]

Baddeleyite, ZrO2

Cathodoluminescence microscope

Cool Early Earth

Earliest known life forms

Hadean zircon

Heavy mineral sands ore deposits

History of Earth

Ilmenite

Cerium anomaly

References[edit]

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.

^ a b c d Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1995). "Zircon" (PDF). Handbook of Mineralogy. Vol. II (Silica, Silicates). Chantilly, VA, US: Mineralogical Society of America. ISBN 978-0962209710.

^ "Zircon: Mineral information, data and localities". Mindat.org. Retrieved October 19, 2021.

^ "Zircon Mineral Data". Webmineral. Retrieved October 19, 2021.

^ a b Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20th ed.). ISBN 0-471-80580-7.

^ Erickson, Timmons M.; Cavosie, Aaron J.; Moser, Desmond E.; et al. (2013). Abstract. "Correlating planar microstructures in shocked zircon from the Vredefort Dome at multiple scales: Crystallographic modeling, external and internal imaging, and EBSD structural analysis" (PDF). American Mineralogist. 98 (1): 53–65. Bibcode:2013AmMin..98...53E. doi:10.2138/am.2013.4165. S2CID 67779734.

^ "zircon". CollinsDictionary.com. HarperCollins. Retrieved April 29, 2018.

^ "zircon". The American Heritage Dictionary of the English Language (5th ed.). HarperCollins.

^ "zircon". Merriam-Webster.com Dictionary. Retrieved April 29, 2018.

^ Stwertka, Albert (1996). A Guide to the Elements. Oxford University Press. pp. 117–119. ISBN 978-0-19-508083-4.

^ Harper, Douglas. "zircon". Online Etymology Dictionary.

^ "Hyacinth (gem)". Encyclopædia Britannica. Encyclopædia Britannica Inc. Retrieved October 7, 2016.

^ Nesse, William D. (2000). Introduction to mineralogy. New York: Oxford University Press. pp. 313–314. ISBN 9780195106916.

^ a b c Jackson, Robert A.; Montenari, Michael (2019). "Computer modeling of Zircon (ZrSiO4)—Coffinite (USiO4) solid solutions and lead incorporation: Geological implications". Stratigraphy & Timescales. 4: 217–227. doi:10.1016/bs.sats.2019.08.005. ISBN 9780128175521. S2CID 210256739 – via Elsevier Science Direct.

^ Nesse 2000, pp. 93–94.

^ "Zircon gemstone information". www.gemdat.org. Retrieved April 29, 2018.

^ Garver, John I.; Kamp, Peter J.J. (2002). "Integration of zircon color and zircon fission-track zonation patterns in orogenic belts: Application to the Southern Alps, New Zealand". Tectonophysics. 349 (1–4): 203–219. Bibcode:2002Tectp.349..203G. CiteSeerX 10.1.1.570.3912. doi:10.1016/S0040-1951(02)00054-9.

^ Nesse 2000, p. 313.

^ Nielsen, Ralph (2000). "Zirconium and Zirconium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a28_543. ISBN 978-3527306732.

^ Davis, Sergio; Belonoshko, Anatoly; Rosengren, Anders; Duin, Adri; Johansson, Börje (January 1, 2010). "Molecular dynamics simulation of zirconia melting". Open Physics. 8 (5): 789. Bibcode:2010CEJPh...8..789D. doi:10.2478/s11534-009-0152-3. S2CID 120967147.

^ "Products". Mineral Commodities Ltd. Archived from the original on October 7, 2016. Retrieved August 8, 2016.

^ Nesse 2000, p. 314.

^ Blatt, Harvey; Middleton, Gerard; Murray, Raymond (1980). Origin of sedimentary rocks (2d ed.). Englewood Cliffs, N.J.: Prentice-Hall. pp. 321–322. ISBN 0136427103.

^ Brauns, Reinhard (1912). The Mineral Kingdom (Volume 1). Translated by Leonard James Spencer. J.F. Schreiber. p. 217.

^ Oliver Cummings Farrington (1903). Gems and Gem Minerals. A.W. Mumford. p. 109.

^ L.J. Spencer (1905). Report of the Seventy-Fourth Meeting of the British Association for the Advancement of Science. John Murray. pp. 562–563.

^ a b "Physical & Optical Properties of Zircon". Colored Gemstones Guide. Retrieved October 19, 2021.

^ Van Westrenen, Wim; Frank, Mark R.; Hanchar, John M.; Fei, Yingwei; Finch, Robert J.; Zha, Chang-Sheng (January 2004). "In situ determination of the compressibility of synthetic pure zircon (ZrSiO4) and the onset of the zircon-reidite phase transition". American Mineralogist. 89 (1): 197–203. Bibcode:2004AmMin..89..197V. doi:10.2138/am-2004-0123. S2CID 102001496.

^ Nesse 2000, pp. 313–314.

^ Hurlbut & Klein 1985, p. 454.

^ Staff (June 2007). "Dubbo Zirconia Project Fact Sheet June 2014" (PDF). Alkane Resources Limited. Archived from the original (PDF) on February 28, 2008. Retrieved September 10, 2007.

^ "The Mineral Sands Industry Factbook" (PDF). Archived from the original (PDF) on August 18, 2016.

^ "Heavy Minerals Mining in Africa – Titanium And Zirconium". Archived from the original on May 28, 2008. Retrieved August 8, 2016.

^ "Zircons – Application Note". DELMIC. Retrieved February 10, 2017.

^ Cawood, P.A.; Hawkesworth, C.J.; Dhuime, B. (October 2012). "Detrital zircon record and tectonic setting". Geology. 40 (10): 875–878. Bibcode:2012Geo....40..875C. doi:10.1130/G32945.1. hdl:10023/3575.

^ a b Wilde, Simon A.; Valley, John W.; Peck, William H.; Graham, Colin M. (2001). "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago". Nature. 409 (6817): 175–178. Bibcode:2001Natur.409..175W. doi:10.1038/35051550. PMID 11196637. S2CID 4319774.

^ Mojzsis, Stephen J.; Harrison, T. Mark; Pidgeon, Robert T. (2001). "Oxygen-isotope evidence from ancient zircons for liquid water at the Earth's surface 4,300 Myr ago". Nature. 409 (6817): 178–181. doi:10.1038/35051557. PMID 11196638. S2CID 2819082.

^ Valley, JW; Peck, WH; King, EM; Wilde, SA (2002). "A cool early Earth". Geology. 30 (4): 351–354. Bibcode:2002Geo....30..351V. doi:10.1130/0091-7613(2002)030<0351:ACEE>2.0.CO;2.

^ Valley, JW; Lackey, JS; Cavosie, AJ (2005). "4.4 billion years of crustal maturation: Oxygen isotopes in magmatic zircon". Contributions to Mineralogy and Petrology. 150: 561–580. doi:10.1007/s00410-005-0025-8. S2CID 53118854.

^ Ushikubo, Takayuki; Kita, Noriko T.; Cavosie, Aaron J.; Wilde, Simon A.; Rudnick, Roberta L.; Valley, John W. (2008). "Lithium in Jack Hills zircons: Evidence for extensive weathering of Earth's earliest crust". Earth and Planetary Science Letters. 272 (3–4): 666–676. Bibcode:2008E&PSL.272..666U. doi:10.1016/j.epsl.2008.05.032.

^ "Ancient mineral shows early Earth climate tough on continents". Physorg.com. June 13, 2008.

^ Nemchin, A.; Pidgeon, R.; Whitehouse, M. (2006). "Re-evaluation of the origin and evolution of >4.2 Ga zircons from the Jack Hills metasedimentary rocks". Earth and Planetary Science Letters. 244 (1–2): 218–233. Bibcode:2006E&PSL.244..218N. doi:10.1016/j.epsl.2006.01.054.

^ Cavosie, A.J.; Valley, J.W.; Wilde, S.A. (2005). "Magmatic δ18O in 4400–3900 Ma detrital zircons: A record of the alteration and recycling of crust in the Early Archean". Earth and Planetary Science Letters. 235 (3–4): 663–681. Bibcode:2005E&PSL.235..663C. doi:10.1016/j.epsl.2005.04.028.

^ Valley, JW; Cavosie, AJ; Ushikobo, T; Reinhardt; Lawrence, DF; Larson, DJ; Clifton, PH; Kelly, TF; Wilde, SA; Moser, DE; Spicuzza, MJ (2014). "Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography". Nature Geoscience. 7 (3): 219–223. doi:10.1038/ngeo2075.

^ a b Borenstein, Seth (October 19, 2015). "Hints of life on what was thought to be desolate early Earth". Excite. Yonkers, NY: Mindspark Interactive Network. Associated Press. Archived from the original on October 23, 2015. Retrieved October 8, 2018.

^ Bell, Elizabeth A.; Boehnke, Patrick; Harrison, T. Mark; Mao, Wendy L. (2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon". Proceedings of the National Academy of Sciences. 112 (47): 14518–14521. Bibcode:2015PNAS..11214518B. doi:10.1073/pnas.1517557112. PMC 4664351. PMID 26483481.

Further reading[edit]

John M. Hanchar & Paul W. O. Hoskin, eds. (2003). "Zircon". Reviews in Mineralogy and Geochemistry (Mineralogical Society of America monograph). 53. ISBN 0-939950-65-0.

D. J. Cherniak & E. B. Watson (2000). "Pb diffusion in zircon". Chemical Geology. 172 (1–2): 5–24. Bibcode:2001ChGeo.172....5C. doi:10.1016/S0009-2541(00)00233-3.

A. N. Halliday (2001). "In the beginning…". Nature. 409 (6817): 144–145. doi:10.1038/35051685. PMID 11196624. S2CID 4339433.

Hermann Köhler (1970). "Die Änderung der Zirkonmorphologie mit dem Differentiationsgrad eines Granits". Neues Jahrbuch für Mineralogie - Monatshefte. 9: 405–420.

K. Mezger & E. J. Krogstad (1997). "Interpretation of discordant U-Pb zircon ages: An evaluation". Journal of Metamorphic Geology. 15 (1): 127–140. Bibcode:1997JMetG..15..127M. doi:10.1111/j.1525-1314.1997.00008.x. S2CID 129846813.

J. P. Pupin (1980). "Zircon and Granite petrology". Contributions to Mineralogy and Petrology. 73 (3): 207–220. Bibcode:1980CoMP...73..207P. doi:10.1007/BF00381441. S2CID 96470918.

Gunnar Ries (2001). "Zirkon als akzessorisches Mineral". Aufschluss. 52: 381–383.

G. Vavra (1990). "On the kinematics of zircon growth and its petrogenetic significance: a cathodoluminescence study". Contributions to Mineralogy and Petrology. 106 (1): 90–99. Bibcode:1990CoMP..106...90V. doi:10.1007/BF00306410. S2CID 140566387.

John W. Valley; William H. Peck; Elizabeth M. King; Simon A. Wilde (2002). "A Cool Early Earth". Geology. 30 (4): 351–354. Bibcode:2002Geo....30..351V. doi:10.1130/0091-7613(2002)030<0351:ACEE>2.0.CO;2. Archived from the original on March 4, 2005. Retrieved April 11, 2005.

G. Vavra (1994). "Systematics of internal zircon morphology in major Variscan granitoid types". Contributions to Mineralogy and Petrology. 117 (4): 331–344. Bibcode:1994CoMP..117..331V. doi:10.1007/BF00307269. S2CID 128459636.

External links[edit]

Wikimedia Commons has media related to Zircon.

Geochemistry of old zircons. Archived April 12, 2007, at the Wayback Machine.

Mineral galleries (archived 7 April 2005)

GIA Gem Encyclopedia – Zircon Online articles and information on zircon history, lore, and research

Zircon Industry Association

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Zircon: Gemstone, December Birthstone, Ore of Zirconium.

Zircon: Gemstone, December Birthstone, Ore of Zirconium.

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Home » Minerals » Zircon

Zircon

Used as a gemstone for over 2000 years. Today it is the primary ore of zirconium.

Article by: Hobart M. King, PhD, RPG

Faceted Zircon: A collection of natural and heat-treated zircons in a range of colors. Starting at top right and going clockwise: rose, peach, yellow, green, blue, honey, white, champagne, cognac, and mocha. These stones are about 5 millimeters in size and weigh approximately 7.47 carats total. The white, blue, green, yellow, peach and rose colors have been produced by heat treatment.

What Is Zircon?

Zircon is a zirconium silicate mineral with a chemical composition of ZrSiO4. It is common throughout the world as a minor constituent of igneous, metamorphic, and sedimentary rocks.

Zircon is a popular gemstone that has been used for nearly 2000 years. Today it serves as a modern birthstone for the month of December.

Zircon occurs in a wide range of colors and has a brightness and fire that rivals those of diamond. Colorless zircon is sometimes used as a lower-cost alternative for diamond. Zircon should not be confused with cubic zirconia, which is a man-made material.

Zircon is present in most soils and clastic sediments. Zircon-rich sediments are mined and the recovered zircon is used to produce zirconium metal and zirconium dioxide. These are used in a wide variety of manufactured products and industrial processes.

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Table of Contents

What Is Zircon?

Geologic Occurrence Of Zircon

Zircon as a Gemstone

Zircon in Tanning and Nail Salons

Zircon Mining

Zircon, Zirconium, Zirconia & CZ

Industrial Uses of Zircon

Zircon and Radioactive Decay

Zircon Gem Rough: Stream-rounded crystals of zircon from an alluvial deposit in Australia. Although brown zircon is not highly marketable, much of it can be altered to a rich blue color by heating in a reducing atmosphere to between 900 and 1000 degrees Celsius. These stones range from about 5 to 10 millimeters in size.

Geologic Occurrence Of Zircon

Zircon is a primary accessory mineral in most granitic rocks. It is also present in gneiss and other rocks derived from the metamorphism of zircon-bearing igneous rocks. Zircon is so common and widely distributed across the rocks of Earth's surface that it could be considered to be a ubiquitous mineral. However, zircon is usually not noticed in rocks and sediments because of its very small particle size. Grains of zircon over a few millimeters in size are rare - they are usually under one millimeter in size. It is one of Earth's most common but most overlooked minerals.

Zircon is highly resistant to chemical alteration and abrasion. When rock units containing zircon are weathered and their sediments are eroded, enormous numbers of tiny zircon crystals are dispersed. These can persist in soils, sediments, and sedimentary rocks for millions - even billions - of years. They can survive several cycles of uplift, weathering, erosion and deposition.

Some of the largest crystals of zircon are formed in pegmatites, carbonate igneous rocks known as carbonatites, and in limestones altered by hydrothermal metamorphism. These large zircons are sometimes of high clarity and suitable for use as gemstones.

Zircon Crystal: A small cluster of nicely-formed zircon crystals which clearly demonstrate that zircon is a member of the tetragonal crystal system. The four-sided crystals are prismatic with a square cross-section and terminate with a pyramid. The largest crystal in the cluster is about 1.7 centimeters in length. Specimen from Mt. Malosa, Malawi.

Physical Properties of Zircon

Chemical Classification

Silicate

Color

Usually yellow, brown, or red. Also colorless, gray, blue, and green.

Streak

Colorless. Usually harder than the streak plate.

Luster

Vitreous to adamantine, sometimes oily.

Diaphaneity

Translucent to transparent

Cleavage

Imperfect

Mohs Hardness

6 to 7.5

Specific Gravity

4.6 to 4.7

Diagnostic Properties

Hardness, luster, specific gravity

Chemical Composition

ZrSiO4

Crystal System

Tetragonal

Uses

Ore of zirconium metal, ore of zirconium dioxide, whitening agents, white pigment, gemstones, radiometric dating.

Zircon as a Gemstone

Zircon has been used as a gemstone for over 2000 years. Its very high dispersion and refractive index give it a brilliance and fire that rival those of diamond. For that reason, colorless faceted zircon has been used as both a popular and fraudulent substitute for diamond.

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Gemologists and many knowledgeable jewelers are able to distinguish zircon from diamond with a quick examination. To do this they look into the stone, through the table facet, and focus on the pavilion facet junctions, with a 10x loupe. The pavilion facet junctions should appear as double-images caused by zircon's double-refraction. Diamond is singly refractive and will not show doubling of features within the stone. This same test can be used to distinguish zircon from cubic zirconia.

Zircon is a popular gem because it is available in a variety of pleasing colors. Most natural zircons are yellow, red, or brown. Heating and irradiation can be used to produce colorless, blue, green, and many other zircon colors. Blue is the most popular zircon color. About 80% of the zircons sold today are blue.

Although it is not as durable as diamond, zircon has good physical durability as a gem. It has a hardness of 6 to 7.5 and imperfect cleavage. That combination makes it suitable for most gemstone uses that include rings, earrings, pendants, brooches and other jewelry. Some zircon, especially gems that have been heat treated, can be brittle. The facet edges of these gems are susceptible to nicks and chipping.

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Zircon in Tanning and Nail Salons

Most blue zircon sold in jewelry today is produced by heat treating brown zircon in a reducing atmosphere to 900 to 1000 degrees Celsius. Some people have damaged these blue zircons by exposing them to ultraviolet radiation in tanning beds or under ultraviolet lamps used to cure acrylic fingernail adhesives. The blue color can degrade to brown with just minutes of exposure. The color of some of these gems have been restored by exposure to low wattage incandescent light. To avoid ruining a nice gem, remove jewelry at tanning and nail salons. [1]

Zircon Concentrate Production: Zircon mineral concentrates are produced by mining heavy mineral sands from land- and marine-based deposits. Australia, South Africa, China, Indonesia, Mozambique, India, Ukraine, Sri Lanka, Madagascar, Brazil, Kenya and several other countries were producing zircon concentrates in 2014. [2]

Heavy Mineral Mining: Photo of the Concord heavy-mineral-sands mine in south-central Virginia. Weakly consolicated Pliocene-age sand and silt deposits here contain about 4% by weight heavy minerals. A separation plant is used to recover ilmenite, leucoxene, rutile, and zircon. [3]

Zircon Mining

Zircon has been mined from stream gravels for over 2000 years. This early mining of zircon was mainly to obtain nice crystals for use as gemstones. Today, most zircon is produced by mining or dredging zircon-rich sediments. These sediments can be in beach, littoral, or alluvial deposits.

Zircon has a specific gravity of 4.6 to 4.7, which is much higher than the typical detrital sediment grain that is between 2.6 and 2.8. This specific gravity difference allows zircon grains to be recovered from the sediments by mechanical separation. Specific gravity separation methods make it possible to profitably recover zircon and other heavy minerals at an ore grade of just a few percent. Zircon is often a coproduct at mining/processing operations where ilmenite and rutile are being mined for titanium. In the United States, zircon is mined in Virginia, Georgia, North Carolina and Florida.

Industrial-grade zircon is mined from land- and marine-based deposits of alluvial origin in many parts of the world. Australia, South Africa, China, Indonesia, Mozambique, India, Ukraine, Sri Lanka, Madagascar, Brazil, Kenya and several other countries were important producers in 2014. These alluvial deposits contain mainly sub-millimeter grains of zircon derived from the weathering of granitic rocks.

Gem-grade zircon has been produced from alluvial deposits in Sri Lanka, Cambodia, Myanmar, and Vietnam for hundreds of years. More recent gem-grade deposits are in Australia, Nigeria, and Madagascar. Deposits mined for gem-grade zircon must contain crystals at least several millimeters in size with good clarity. They are typically derived from the weathering of carbonate rocks and other rock types associated with hydrothermal activity. Some of the best gem-grade zircon crystals are mined directly from cavities in pegmatite.

The best way to learn about minerals is to study with a collection of small specimens that you can handle, examine, and observe their properties. Inexpensive mineral collections are available in the Geology.com Store. Image copyright iStockphoto / Anna Usova.

Zircon, Zirconium, Zirconia, CZ

There is much public confusion between four materials: zircon, zirconium, zirconia and cubic zirconia. Summary definitions of these terms are provided below.

Zircon is a naturally occurring mineral with a chemical composition of ZrSiO4.

Zirconium is a silvery white metal and a chemical element. It has an atomic number of 40 and an atomic symbol of Zr.

Zirconia is the white crystalline oxide of zirconium with a chemical composition of ZrO2. A naturally occurring, but rare, form of ZrO2 is the mineral baddeleyite.

Cubic Zirconia is a synthetic gemstone with an appearance that is very similar to diamond. It sells for a tiny fraction of the cost of diamond and has historically been the most commonly used diamond simulant.

All of these materials are related. Zirconium, zirconia and cubic zirconia are all produced from industrial-grade zircon.

Industrial Uses of Zircon

Zircon References

[1] Reversible Color Modification of Blue Zircon by Long-Wave Ultraviolet Radiation, by Nathan D. Renfro, Gems & Gemology, Volume 52, Number 3, Fall 2016.

[2] Zircon and Hafnium, by George M. Bedinger, 2014 Minerals Yearbook, United States Geological Survey, August 2016.

[3] Deposit Model for Heavy-Mineral Sands in Coastal Environments, by Bradley S. Van Gosen, David L. Fey, Anjana K. Shah, Philip L. Verplanck, and Todd M. Hoefen, Mineral Deposit Models for Resource Assessment, Scientific Investigations Report 2010–5070–L, United States Geological Survey, 2014.

[4] Mineville, Eastern Adirondacks – Geophysical and Geologic Studies, by Anjana Shah, article on the United States Geological Survey website, last accessed August 2022.

Zircon sand has a low expansion coefficient and is very stable at high temperatures. It is used as a refractory material in many foundry and casting applications. One of its most common uses is in the production of ceramics.

Zirconium dioxide (zirconia) is produced by heating zircon sand to a high enough temperature to break down the zircon molecule. In powdered form, zirconium dioxide is bright white, highly reflective and thermally stable. It is used as an opacifier, whitening agent, and pigment in glazes and stains used on ceramics and pottery. Yttria-stabilized zirconia is used to manufacture cubic zirconia, fiber optic components, refractory coatings, ceramics, dentures and other dental products.

Zircon serves as the primary ore of zirconium metal. Zirconium is used in a variety of metal products that require a resistance to heat and corrosion. It is used to make high-performance alloys, specialty steel, lamp filaments, explosive primers, computer equipment and many electronics components.

Billion-year-old zircons: These zircon grains were hand-picked from a quartz-albite rock collected in Essex County, New York. This petrographic microscope transmitted light image reveals cracks, inclusions, and age “zones” throughout the grains. The cores and rims of the zircon grain reflect magmatic and tectonic events that occurred within the region about 1-1.15 billion years ago. [4]

Zircon and Radioactive Decay

Many zircon crystals contains trace amounts of uranium and thorium. These radioactive elements were incorporated into the zircon at the time of crystallization. They convert into their decay products at a steady rate. The ratio of parent materials to daughter products can be used to estimate the time of crystallization. Using this method, the oldest mineral grains in the world are zircon crystals found in Australia. They are estimated to be about 4.4 billion years old.

When radioactive elements in zircon crystals or nearby materials decay, radiation is emitted. The zircon crystal can be damaged by this radiation. Some zircon has been so damaged by exposure to this radiation that it no longer retains the clarity and optical properties of an attractive gem material. This is why some zircon is not suitable for use as a gem.

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Zircon Value, Price, and Jewelry Information - Gem Society

on Value, Price, and Jewelry Information - Gem SocietyMEMBERSHIPSearchLearning CenterGemologyScience, tools, identification, treatment, valuation & grading of gemsJewelry & LapidaryGemstone jewelry settings, metals, tools, cutting & faceting stonesGemstone EncyclopediaList of all gemstones from A-Z with in-depth information for eachGem Photo GalleryThousands of gem photos searchable by various properties.Diamond Buying AdviceEverything you need to know about buying your perfect diamondBirthstonesLearn more about these popular gemstones, their meaning & about buying birthstone jewelryGem PricingGemstone Price GuidesPrice guidance on over 70 types of gemstonesExpert Buying GuidesIn-depth guides to quality factors of the 40 most popular gemstonesCoursesOverviewMini CoursesProfessional Gemologist CertificationDiamond Specialist CertificationCommunityGem BusinessesView AllAppraisalsAuctionsGem CuttingGem TreatingGemological LaboratoriesGemology Supplies & EquipmentGemstonesInformational ResourcesJewelryLapidary Supplies & EquipmentRough Gems & Mineral SpecimensAboutAbout IGSAdvertiseContact UsFAQSupportPressZircon Value, Price, and Jewelry InformationDon’t be confused by the name. Zircon is a natural, magnificent, and underrated gemstone that has been worn and treasured since ancient times. It’s not cubic zirconia. Available in many colors, zircon is one of the modern December birthstones and will look wonderful in jewelry if set carefully.9 Minute ReadHomeGemstonesZircon Value, Price, and Jewelry InformationBy Joel E. Arem, Ph.D., FGA, Donald Clark, CSM IMG, Barbara Smigel, PhD. GG, International Gem SocietyDon’t be confused by the name. Zircon is a natural, magnificent, and underrated gemstone that has been worn and treasured since ancient times. It’s not cubic zirconia. Available in many colors, zircon is one of the modern December birthstones and will look wonderful in jewelry if set carefully.

This yellowish round 4.92-ct zircon displays this gemstone’s high dispersion very well. © All That Glitters. Used with permission.Start an IGS Membership todayfor full access to our price guide (updated monthly).More About MembershipZircon ValueZircons come in many colors, but blue is perhaps the most popular and expensive. However, almost all blue zircon is heat treated.

These matched blue oval brilliant-cut zircons have been heat treated. 3.62 ctw, 5.8 x 4.2 mm, Cambodia. © The Gem Trader. Used with permission.

Green is the rarest natural color.

Bright green cushion-cut zircon, 5.61 cts. © All That Glitters. Used with permission.

To learn more about zircon quality factors, consult our zircon buying guide.

Zircons: Sri Lanka (19.03, 17.43, 14.20, 9.26 // 4.36, 11.26, 15.70), Cambodia (5.56) // Sri Lanka (8.92, 16.63, 7.77, 5.34). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Zircon color suite from about 5 to 35 carats: yellow, green, and orange from Sri Lanka; red from Africa; blue from Cambodia. © Joel E. Arem, PhD, FGA. Used with permission.What's the Difference Between Zircon and Cubic Zirconia?Although zircon and cubic zirconia (CZ) share a similar name, they are completely different gemstones. Gemologists define gem species by their chemical formula and crystal system. Zircon has a chemical formula of ZrSiO­4 + Fe, U, Th, Hf and forms in the tetragonal crystal system. On the other hand, CZ has a chemical formula of ZrO2 and forms in the isometric or cubic crystal system. They both contain some zirconium and oxygen but otherwise have different physical and optical properties.While the CZ you may find in jewelry is all lab-created, the zircon used for jewelry is most likely a mined, naturally occurring mineral.Another coincidence might lead to some confusion between zircon and CZ. Both materials have been used extensively as diamond simulants or lookalikes. (Of course, diamonds are another distinct gem species).How Similar are Zircons and Diamonds?As a species, zircon has many interesting characteristics. Some, such as its high refractive index (RI) and dispersion, seem to have made it the "natural choice" for a diamond simulant, so to speak. When properly cut, colorless zircons can make very convincing diamond imitations and even outshine mediocre diamonds. (Interestingly, despite a long history as a diamond substitute, zircon is actually rarer than diamond)."Fashion flowers" colorless zircon ring. Photo by Mathilda Samuelsson. Licensed under CC By-SA 2.0.However, the imitation only goes so far. Poor cutting can make these gems appear relatively dull and lifeless. Although zircons have a respectable hardness for jewelry stones (6 to 7.5), that falls well short of diamond's famous 10. Zircons are far more susceptible to scratching than diamonds. They also have a very brittle tenacity, lower than that of most gemstones. This means their facet edges tend to chip and wear easily.This blue zircon shows notable wear on its facet edges as well as poor meets. 2.65 cts, 7 x 5 x 5 mm, Africa. Image courtesy of liveauctioneers.com and Jasper52.The most obvious optical difference between zircons and diamonds is birefringence (double refraction). While diamonds have no birefringence, zircons have such a strong birefringence that gem cutters must orient the table of the stone to the optic axis. Otherwise, the interior may look fuzzy due to facet image doubling.Does Zircon Make a Good Jewelry Stone?Zircons are more than just diamond simulants. They're stunning gemstones in their own right and occur naturally in a wide range of colors. Heat treatments also produce many additional colors.Zircons in many colors. Photo © Joel E. Arem, PhD, FGA. Used with permission.However, any zircons in jewelry should be worn carefully to prevent damage. As ring stones, they need protective settings due to their brittle tenacity. Pendants, brooches, and earrings are safer jewelry choices.You should usually reserve zircon jewelry for occasional wear. Nevertheless, they can also make beautiful and unusual engagement ring stones. To learn more about choosing zircons for engagement rings, consult our article on delicate engagement ring stones.Zircon and diamond jewelry. Photo © Joel E. Arem, PhD, FGA. Used with permission.Poorly cut zircons may also benefit from expert custom recutting. Take a look at the before-and-after photos of zircons in this article on gem recutting and repair.Natural pink step-cut zircon, 2.13 cts. Image courtesy of liveauctioneers.com and Jasper52.Zircon Color and Trade NamesHyacinth or JacinthTransparent reddish brown zircons.  Historically, this name was also applied to hessonite, a reddish orange variety of garnet.StarliteRich, slightly greenish blue, heated zircons. Although you may still encounter this marketing name, it never really caught on.Jargoon or JargonLight yellow to colorless zircons.Light yellow zircons like these have been called "jargoons." Poudrette quarry Mont Saint-Hilaire, Rouville RCM, Montérégie, Québec, Canada. Photo by Modris Baum. Public domain.BeccariteGreen zircons.MelichrysosYellow zircons.Zircon rough and cut set. Crystal specimen: 4.0 x 1.2 x 1.1 cm; oval brilliant-cut gem: 14.11 x 11.25 mm, 11.40 cts. Ambilipitiya, Sri Lanka. © Rob Lavinsky, www.iRocks.com. Used with permission.SparkliteColorless zircons.StremliteBlue zircons.Color Change ZirconsColor change has been documented in zircons. In a 2021 GIA report, a zircon showed green color in incandescent, fluorescent, and warm LED light (2700 K) and grayish purple in daylight and cool LED light (6500 K). The report noted this rare phenomena is occasionally found in zircons from Mogok, Myanmar.This mixed cushion-cut zircon from Myanmar appears blueish green in incandescent light and purple in daylight. 1.77 cts, 7.6 x 5.5 mm. © The Gem Trader. Used with permission.Tenebrescence (reversible photochromism) has also been documented in zircons. A 2014 GIA article noted two distinct cases: zircons have been observed that turn orange in darkness but faded to near colorless when exposed to light; in another study, a reddish orange zircon darkened to brown when exposed to shortwave UV light, but its color returned when placed in darkness.This vivid orange, round brilliant-cut zircon turns orangish brown when exposed to the UV in daylight. The change occurs in only a few minutes. The bright orange color returns after a few days in low light or darkness. 2.51 cts, 8.1 mm, Myanmar. © The Gem Trader. Used with permission.Misleading Names for ZirconColorless zircons have been sold as "Matara " or "Matura diamonds" and "Ceylon diamonds." Although zircons are used to simulate diamonds, selling them as actual diamonds is unethical.Blue zircons have been deceptively sold as "Siam aquamarines."Although zircons are rarer than both diamonds and aquamarines, these gems are more popular than zircons. Thus, some dishonest vendors will use these misleading names to sell zircons more easily.For more examples of deceptively labeled gems, see our List of False or Misleading Gemstone Names.Is Zircon Radioactive?Some zircon crystals pick up small amounts of radioactive uranium and thorium during their natural growth. This radiation is barely measurable. However, over millions of years, the radiation breaks down the crystal structure. These stones, usually green, become metamict. That is, they are materials that have lost their crystalline structure and become amorphous due to radiation. Metamict zircons have a lower RI and brilliance than the crystalline type.Zircon is classed as high, immediate or medium, or low based on its level of deterioration. (These are also called alpha, beta, and gamma). The classes are easy to distinguish because the properties change in an even progression.High zircon is fully crystalline and has the highest properties.Intermediate zircon is material slightly damaged by radiation.Low zircon is metamict.Interestingly, dispersion is the same for both high and low varieties while other optical properties vary. Low zircon usually has a cloudy texture.Low ZirconIntermediateHigh ZirconColorsGreen, brown, orangeBrownish green, dark redColorless, blue, brownish orangeRIo = 1.78--1.815 (almost isotropic)o = 1.83-1.93e = 1.84-1.970o = 1.92-1.94 (often 1.925)e = 1.97-2.01 (often 1.984)Birefringence0-0.0080.008-0.0430.036-0.059 (usually 0.059)Specific Gravity3.95-4.20 (usually about 4.0)4.08-4.604.6-4.80 (usually 4.70)Red zircon, 4.04 cts, Nigeria. © Joel E. Arem, PhD, FGA. Used with permission.Is Zircon Jewelry Safe to Wear?Although most zircons are safe to wear, some may have mild levels of natural radioactivity, especially the low or metamict variety. Consumers may wish to have a gem lab measure the radioactivity of green, brown, or orange (metamict) zircons.In addition to standard lapidary precautions, gem cutters should check the radioactivity of zircons before working on them.Identifying ZirconsThe most obvious way to distinguish a zircon presented as a substitute diamond from an actual diamond is by the former's birefringence.Zircon's high birefringence makes this 4.57-ct round brilliant-cut stone appear fuzzy. Image courtesy of liveauctioneers.com and Jasper52.All classes of faceted zircon can be identified by abraded or worn facet edges.LuminescenceZircon has variable fluorescence. Some material is inert. Other crystals glow intensely. Mustard yellow and yellow-orange are typical fluorescent colors under shortwave (SW) ultraviolet (UV) light. Some zircons glow dull yellow in longwave (LW) UV light and may also phosphoresce. Zircon may be whitish, yellow, greenish, or violet-blue under X-rays.Red to orange red: inert to strong, yellow to orange (SW).Yellow to orangish yellow: inert to moderate yellow to orange (LW and SW).Green: usually inert.Blue: inert to moderate, light blue (LW).Brown: inert to very weak red (SW).Golden red zircons on a biotite and hornblende matrix, with yellow-orange fluorescence under UV light. 7.6 x 4.4 x 3.9 cm, Seiland Island, Alta, Finnmark, Norway. © Rob Lavinsky, www.iRocks.com. Used with permission.Absorption SpectrumMost zircons show a strong absorption pattern that's very useful for identification. Green stones from Myanmar may show more than forty lines, while orange gems from New South Wales, Australia may show only a few lines. Low zircon and heat-treated stones have a weaker display.Most zircons show a strong line at 6535 even in types where a strong spectrum is otherwise absent. They may also have lines at 6910, 6830, 6625, 6605, 6210, 6150, 5895, 5625, 5375, 5160, 4840, 4600, and 4327.Heat-treated stones (colorless, blue, and golden brown) may show only one fine line at 6535 and also a weaker line at 6590.Red and brown zircons may display no spectrum at all.Are There Synthetic Zircons?Scientists have synthesized crystalline zircons via the flux method for research purposes. However, there's no known jewelry use for this lab-created material. Nevertheless, you may find "synthetic zircons" for sale online. It's not clear if this material is actually lab-created zircon or perhaps the more commonly found and well-known CZ.While the CZ used for jewelry is a lab-created material, it's not synthetic zircon. Whether natural or lab-made, they remain distinct gem species.Do Zircons Receive Gem Treatments?Almost all colorless and blue zircons have been heat treated. This procedure is undetectable.The popular blue, colorless, and golden yellow shades are usually produced by heating. The stones that yield these lovely colors typically start out naturally as reddish-brown.Zircons with other colors don't commonly receive this heat treatment. Green and yellow colors produced by heating usually have greater stability over time and more resistance to fading from sunlight and UV light than blues produced by heat.Heating helps to crystallize partially metamict zircons. This raises specific gravity and sharpens the absorption spectrum.Heating green Sri Lankan zircon makes it paler in color. Red-brown Sri Lankan material becomes colorless, sometimes reddish violet.Heating red-brown Thai and Cambodian stones turns them colorless, blue, or golden.Brownish stones are often heated either with or without oxygen present to achieve shades of blue and golden yellow.Brown zircons with high uranium content may turn green with heating.Zircons: blue stone from Cambodia, all others from Sri Lanka, ~ 5-30 carats. Photo © Joel E. Arem, PhD, FGA. Used with permission.Where are Zircons Found?Zircon is found all over the world, but gem-quality crystals are rare. Southeast Asia is the primary sources of gem-quality zircons.Sri Lanka produces material in all colors in gravels, including rare cat's eyes.Zircons may rarely display chatoyancy, like this brownish gray cat's eye. Round cabochon, 5.48 cts, 8.1 mm, Sri Lanka. © The Gem Trader. Used with permission.Cambodia is the chief source of material that heat treats to colorless and blue.Zircons: Cambodia (~ 25, 40). Photo © Joel E. Arem, PhD, FGA. Used with permission.Myanmar produces yellowish and greenish stones in gem gravels with ruby. These stones have complex absorption spectra.Thailand is one of the most important commercial sources of gem-grade zircon.Other notable gem-quality sources include the following localities:New South Wales, Australia: fine gem material (orange).Quebec and Ontario, Canada: dark, opaque crystals up to 15 pounds, yield only tiny gems.France: red crystals at Espaly, St. Marcel.Emali, Tanzania: white zircon pebbles.United States: Colorado; Maine; Massachusetts; New Jersey; New York; Oklahoma; South Dakota; Texas.Brazil; China; Germany; India; Madagascar; Mexico; Nigeria; Norway; North Korea; Pakistan; Russia; South Korea; Vietnam.Oval-cut, 9.44-ct pink zircon, Orissa, India. © Joel E. Arem, PhD, FGA. Used with permission.Stone SizesThe largest zircon gems come from Southeast Asian gem gravels.Smithsonian Institution (Washington, DC): 118.1 (brown, Sri Lanka); 97.6 (yellow-brown, Sri Lanka); 75.8 (red-brown, Myanmar); 64.2 (brown, Thailand); 23.5 (green, Sri Lanka); 23.9 (colorless, Sri Lanka); 103.2 (blue, Thailand).Geology Museum, London: 44.27 (blue); 22.67 (golden); 14.34 (red); 21.32 (white).Royal Ontario Museum (Toronto, Ontario, Canada): 23.8 (brown); 17.80 (blue); 61.69 (blue, step-cut).American Museum of Natural History (New York): 208 (greenish blue, Sri Lanka).Zircons: yellow (15.5 cts), blue (23.75 cts). © Joel E. Arem, PhD, FGA. Used with permission.How to Care for Zircon JewelryDue to their brittleness, zircons should never be cleaned with mechanical systems, such as ultrasonic cleaners. Instead, use warm water, mild detergent, and a soft brush.For more care recommendations, consult our gemstone jewelry cleaning guide.Zircons from left: Australia, 5.2 and 3.7 cts; Cambodia, 15.6 cts and 4.25 cts; Australia, 2.35 cts. The blue zircon displays a pronounced pleochroic bowtie. © Joel E. Arem, PhD, FGA. Used with permission.Joel E. Arem, Ph.D., FGADr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world.

Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education. joelarem.com

View All ArticlesDonald Clark, CSM IMGThe late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

View All ArticlesBarbara Smigel, PhD. GGBarbara Smigel is a GIA certified gemologist, facetor, jewelry designer, gem dealer, gemology instructor and creator of the well-regarded educational websites acstones.com and bwsmigel.info.

View All ArticlesInternational Gem SocietyView All ArticlesTable of ContentsWhat's the Difference Between Zircon and Cubic Zirconia?How Similar are Zircons and Diamonds?Does Zircon Make a Good Jewelry Stone?Zircon Color and Trade NamesHyacinth or Jacinth StarliteJargoon or Jargon Beccarite Melichrysos Sparklite StremliteColor Change ZirconsMisleading Names for ZirconIs Zircon Radioactive?Is Zircon Jewelry Safe to Wear?Identifying Zircons LuminescenceAbsorption SpectrumAre There Synthetic Zircons?Do Zircons Receive Gem Treatments?Where are Zircons Found?Stone SizesHow to Care for Zircon JewelryZircon PropertiesAbsorption SpectrumSee "Identifying Zircons."BirefringenceVaries by amount of radioactive damage. 0 (isotropic)-0.059. See "Is Zircon Radioactive?" for more information.BirthstoneDecemberCleavageImperfectColorsReddish brown, yellow, gray, green, red; various other colors induced by heating.CrystallographyTetragonal. Crystals prismatic, pyramidal; often twinned; rounded pebbles.Dispersion0.039 for all zircon types.EnhancementsVirtually all blue zircon is heat treated.EtymologyFrom the Arabic zargun, from the Persian zar for “gold” plus gun for “color.” The name is ancient.

FormulaZrSiO­4 + Fe, U, Th, Hf

FractureConchoidalFracture LusterVitreous to subadamantineHardness6 (Low), 7.5 (High)Heat SensitivityNoneInclusionsAngular zoning and streaks are sometimes seen in the low type. Some silk is seen occasionally, as well as tension cracks and epigenetic cracks stained with iron oxides. Metamict pieces may have bright fissures known as angles.

LuminescenceSee "Identifying Zircons."Luminescence PresentYesLuminescence TypeFluorescent, Phosphorescent, UV-Long, UV-Short, X-ray ColorsLusterVitreous to adamantine; sometimes greasy.OccurrenceIn igneous rocks worldwide, especially granites. Also found as alluvial material.

Optic SignUniaxial +OpticsUniaxial (+).

PhenomenaChatoyancy, color change, tenebrescence (all rare)PleochroismDistinct in blue stones: deep sky blue/colorless to yellowish gray. Red: red/clove brown. Brown: reddish brown/yellowish brown.

Polish LusterVitreous to adamantineRefractive IndexVaries by amount of radioactive damage to its crystal structure. Low (most damaged): 1.78-1.85; Intermediate: 1.85-1.93; High (least damaged): 1.92-2.01. See "Is Zircon Radioactive?" for more information.Special Care InstructionsFacet edges wear off. Use protective settings for ring use.Specific GravityLow 3.95-4.20, Intermediate 4.08-4.60, High 4.60-4.80TransparencyTransparent to opaqueTypical TreatmentsHeat TreatmentVarietiesHyacinth, StarliteVariety ofBest Known GemstonesRelated ArticlesMore ArticlesZircon Buying GuideLong valued for its brilliance, zircon is a natural and affordable beauty. Learn more about the quality factors for this...Read MoreCan You Identify Gems Without Seeing Gemstone Colors?Did you know most gem species can be distinguished without the element of color? Learn the role gemstone colors play...Read MoreBlack Diamond Value, Price, and Jewelry InformationBlack is a color that can say a lot. Wearing black diamond jewelry communicates a sense of unique strength and...Read MoreChameleon Diamond Value, Price, and Jewelry InformationProfessionals will tell you never to trust a trade name used to describe the appearance of a fancy colored diamond....Read MoreLatest ArticlesMore ArticlesParaíba Tourmaline Value, Price, and Jewelry InformationDiscovered in 1989, paraíba tourmalines are among the world’s most prized gemstones. These rare gems are renowned for showing intense...Read MorePrecision Faceting a Story Gemstone: The Faceting ProcessThe faceting process turns rough stones into finished gems. Learn the steps custom faceters take to create unique gemstones that...Read MoreAquamarine Color and Heat TreatmentThere's more to aquamarine color than blue. Most natural stones start blueish green and are heated to blue. Learn the...Read MoreWhat is Gemstone Luster?Gemstone luster describes how a gem's surface looks when it reflects light. Learn the common terms gemologists use for this...Read MoreLatest Community DiscussionsMore DiscussionsTanzanian CorundumRead MoreIs This a Topazolite Garnet?Read MoreNigerian GemstonesRead MoreIs This an Opal?Read MoreNever Stop LearningWhen you join the IGS community, you get trusted diamond & gemstone information when you need it.Become a MemberGet Gemology InsightsGet started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!Email AddressSubmitThe International Gem Society (IGS) is the world's top resource for gem professionals, enthusiasts, and industry content.support@gemsociety.orgLearning CenterGemologyGemstone EncyclopediaJewelry & LapidaryDiamond Buying AdviceGemstone Price GuideExpert Buying GuidesCoursesIGS Mini CoursesProfessional Gemologist CertificationDiamond Specialist CertificationAboutAdvertiseContactFaqSupportPressMembership© 2024 International Gem Society LLC. All rights reserved.Privacy PolicyTerms of UseAffiliate DisclosureAccessibility Statement

Zircon : Properties, Occurrence, Locations, Uses » Geology Science

Zircon : Properties, Occurrence, Locations, Uses » Geology Science

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Home Gemstone Zircon

GemstoneMineralsSilicates Minerals

Zircon

Modified date: 01/02/2024

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Zircon, scientifically known as zirconium silicate (ZrSiO4), is a mineral prized for its versatility and wide-ranging applications. With its remarkable resistance to heat, corrosion, and chemical alteration, zircon finds use in diverse industries. Gem-quality zircons, known for their brilliant luster and dispersion, are sought after in the jewelry market, coming in various colors, including blue and red. In geology, zircon plays a crucial role as a valuable tool for radiometric dating, offering insights into Earth’s history. Additionally, zircon is employed in the manufacturing of refractory materials, ceramics, foundry casting, and nuclear technology, making it a key mineral in modern industrial processes.

What is Zircon? Zircon, scientifically known as zirconium silicate (ZrSiO4), is a naturally occurring mineral found in the Earth’s crust. It is a dense, hard, and durable mineral that typically appears as small, reddish-brown to grayish crystals. Zircon contains the elements zirconium and silicon, along with trace amounts of other elements such as hafnium, uranium, and thorium.

History and Discovery of Zircon: The history of zircon dates back thousands of years. Ancient civilizations used zircon in jewelry and decorative objects due to its brilliant luster and striking appearance. It was often mistaken for a diamond due to its sparkle.

In the 18th century, zircon was officially recognized as a distinct mineral, and its chemical composition was determined. Its name “zircon” is derived from the Persian word “zargun,” which means “gold-colored.”

In more recent history, zircon has gained importance in the field of geology and radiometric dating. Zircon crystals found in igneous rocks have been used to estimate the age of the Earth’s crust and the timing of geological events, making zircon an invaluable tool in understanding Earth’s history.

Importance and Uses of Zircon: Zircon has a wide range of uses across various industries, thanks to its unique properties:

Gemstone and Jewelry: Zircon crystals, when cut and polished, can be used as gemstones in jewelry. They come in a variety of colors, including blue, yellow, and brown, and are prized for their brilliance and fire.

Radiometric Dating: Zircon is crucial in the field of geology for radiometric dating. Zircon crystals often contain small amounts of uranium, which undergo radioactive decay into lead over time. By analyzing the ratio of uranium to lead in zircon crystals, scientists can estimate the age of rocks and minerals, providing insights into geological history and the timing of Earth’s events.

Ceramics and Refractory Materials: Zircon’s high melting point and resistance to corrosion make it a valuable component in ceramics, refractory materials, and crucibles used in high-temperature applications like foundry casting and glass manufacturing.

Zirconium Metal Production: Zirconium, derived from zircon, is used in various industrial applications, including nuclear reactors, chemical processing equipment, and aerospace components due to its excellent heat resistance and corrosion resistance.

Zirconia: Zirconia (zirconium dioxide) is a synthetic material derived from zircon. It is used in dental crowns, cutting tools, and as a high-performance ceramic material in various engineering and medical applications.

Catalysts: Zirconium compounds are used as catalysts in the petrochemical industry for the production of chemicals and plastics.

In summary, zircon is a versatile mineral with a rich history of use in jewelry and a critical role in geology, industrial applications, and advanced materials. Its unique properties and abundance in nature make it an essential resource in various fields.

ContentsGeology and Formation of ZirconGeological occurrence and distributionPhysical and Chemical Properties of ZirconZircon in GemologyIndustrial ApplicationsAnalytical TechniquesLocations of major Zircon deposits worldwide

Geology and Formation of Zircon

Zircon is a mineral with a fascinating geological history and formation process. Understanding its geology and formation provides valuable insights into its properties and significance. Here’s an overview of the geology and formation of zircon:

Formation:

Magmatic Origin: The primary source of zircon is igneous rocks, specifically granitic and syenitic rocks, where it crystallizes from molten magma during the cooling and solidification of these rocks. Zircon forms as tiny crystals within these igneous rocks, often alongside other minerals like quartz and feldspar.

Metamorphic Rocks: Zircon can also be found in metamorphic rocks, where it may have originally formed in igneous rocks and later recrystallized due to high temperature and pressure. This can occur during processes like regional metamorphism.

Geological Setting:

Granitic Pegmatites: Zircon is commonly found in granitic pegmatites, which are coarse-grained veins of granite that form as the final product of the crystallization of magma. Pegmatites often contain large zircon crystals and are famous for yielding gem-quality zircon specimens.

Sedimentary Deposits: Zircon can be transported by erosion and deposited in sedimentary rocks, such as sandstones and conglomerates. These sedimentary zircon grains often have rounded shapes and are used for detrital zircon geochronology to determine the age of sedimentary rocks.

Key Geological Processes:

Crystallization: Zircon crystallizes from magma or forms as small grains in the mineral matrix of igneous rocks. Its crystal structure consists of zirconium, silicon, and oxygen atoms arranged in a tetragonal lattice.

Radiogenic Isotopes: Zircon’s significance in geology stems from its ability to incorporate small amounts of radioactive elements, particularly uranium and thorium, into its crystal structure. Over geological time, these radioactive isotopes decay into stable lead isotopes. By measuring the ratios of uranium and lead isotopes in zircon crystals, scientists can determine the age of the zircon and, by extension, the age of the rock in which it formed.

High Thermal Stability: Zircon is highly resistant to weathering, chemical alteration, and high-temperature conditions. This property allows zircon grains to persist in the Earth’s crust for billions of years, making them valuable in radiometric dating and understanding geological processes.

In summary, zircon is primarily formed in igneous rocks through the crystallization of magma, but it can also occur in metamorphic rocks and sedimentary deposits. Its unique ability to incorporate radioactive elements and its resistance to geological processes make it a critical tool for geologists in dating rocks, reconstructing Earth’s history, and understanding geological phenomena.

Geological occurrence and distribution

Zircon is a mineral that occurs naturally in a wide range of geological settings and can be found in various types of rocks and deposits around the world. Its distribution is influenced by its formation processes and geological history. Here’s an overview of the geological occurrence and distribution of zircon:

1. Igneous Rocks:

Granites: Zircon is commonly associated with granitic rocks and is often found as small crystals within these intrusive igneous rocks. Granite is one of the primary sources of zircon.

Syenites: Similar to granites, zircon can also be found in syenitic rocks, which are igneous rocks with a different mineral composition.

2. Pegmatites:

Granitic Pegmatites: Pegmatites are coarse-grained veins or pockets that form in the final stages of the crystallization of magma. Some pegmatites contain exceptionally large zircon crystals, and these are highly sought after by mineral collectors.

3. Metamorphic Rocks:

Zircon can be found in some metamorphic rocks, especially those formed from the recrystallization of pre-existing zircon-bearing minerals or as a result of regional metamorphism.

4. Sedimentary Deposits:

Sandstones: Zircon grains can be transported by erosion from their primary igneous or metamorphic sources and accumulate in sedimentary rocks like sandstones. Detrital zircons in sandstones can be used for dating the sedimentary rocks and understanding sedimentary basin histories.

Conglomerates: Zircon grains are often found in conglomerate rocks, where they act as durable, rounded pebbles or grains.

5. Placer Deposits:

In some regions, zircon can accumulate in placer deposits through weathering and erosion of primary sources. These deposits are often mined for their zircon content, along with other heavy minerals like garnet and ilmenite.

6. Beach Sands:

Coastal areas may have zircon-rich beach sands. The heavy mineral content of these sands, including zircon, can be economically significant.

7. Volcanic Rocks:

Zircon can also be found in certain volcanic rocks, where it may crystallize during the cooling of lava or volcanic ash.

Distribution: Zircon is distributed worldwide, but some regions are particularly well-known for their zircon deposits:

Australia: Australia is a major producer of zircon, with significant deposits found in Western Australia and Queensland.

Brazil: Brazil is known for its high-quality zircon gemstones, often found in pegmatites.

Sri Lanka: Sri Lanka is famous for its blue and green zircon gemstones.

Madagascar: Madagascar also produces gem-quality zircon, often found in alluvial deposits.

South Africa: South Africa has notable zircon deposits associated with its heavy mineral sands.

Norway: Norway is known for its zircon-bearing granitic rocks.

India: India has zircon-bearing rocks in various states, including Odisha, Tamil Nadu, and Kerala.

United States: Zircon can be found in various U.S. states, including North Carolina, Florida, and Colorado.

Zircon’s widespread distribution and occurrence in various geological settings make it an important mineral in both industrial applications and the study of Earth’s geological history through radiometric dating.

Physical and Chemical Properties of Zircon

Zircon, a naturally occurring mineral, possesses a variety of physical and chemical properties that contribute to its importance in various industrial and geological applications. Here are some of the key physical and chemical properties of zircon:

Physical Properties:

Crystal System: Zircon crystallizes in the tetragonal crystal system, which means its crystal structure has fourfold rotational symmetry.

Hardness: Zircon is relatively hard, typically ranking around 7.5 on the Mohs scale of mineral hardness. This hardness makes it durable and suitable for use as a gemstone and in industrial applications.

Density: Zircon has a relatively high density, with values ranging from approximately 4.6 to 4.7 grams per cubic centimeter (g/cm³). This density contributes to its use as a heavy mineral in placer deposits.

Color: Zircon can come in various colors, including brown, reddish-brown, yellow, green, blue, and colorless. Gem-quality zircons often exhibit vivid colors and high transparency.

Luster: Zircon typically has a high luster, giving it a shiny and reflective appearance when cut and polished. This luster enhances its use as a gemstone.

Cleavage: Zircon exhibits imperfect cleavage along its crystallographic planes, which means it can break along certain directions with distinct cleavage surfaces.

Transparency: Depending on impurities and crystal quality, zircon can range from transparent to translucent.

Dispersion: Gem-quality zircons often display strong dispersion, which is the ability to split white light into its spectral colors. This property gives zircon its “fire” or play of colors.

Chemical Properties:

Chemical Composition: Zircon is a zirconium silicate mineral with the chemical formula ZrSiO4. It consists primarily of zirconium (Zr), silicon (Si), and oxygen (O), with trace amounts of other elements like hafnium (Hf).

Stability: Zircon is highly resistant to chemical weathering and remains stable over geological time periods. It is not easily altered by common geological processes, which makes it a valuable mineral for radiometric dating.

Radiogenic Isotopes: Zircon can incorporate trace amounts of radioactive isotopes such as uranium (U) and thorium (Th) during its crystallization. Over time, these isotopes decay into stable lead (Pb) isotopes. This property is used for radiometric dating of zircon and the rocks in which it occurs.

Zirconia Formation: Zircon can be transformed into zirconia (zirconium dioxide, ZrO2) through high-temperature processes. Zirconia is a versatile ceramic material with various industrial applications.

Heat Resistance: Zircon is highly heat-resistant and can withstand extremely high temperatures without undergoing significant changes, making it suitable for use in refractory materials and high-temperature applications.

Chemical Inertness: Zircon is chemically inert under most conditions, which contributes to its durability and stability in various environments.

In summary, zircon’s physical properties include its crystal system, hardness, density, color, luster, cleavage, transparency, and dispersion. Its chemical properties involve its composition, stability, radiogenic isotopes, ability to form zirconia, heat resistance, and chemical inertness. These properties collectively make zircon valuable in industries such as jewelry, geology, ceramics, and high-temperature applications.

Zircon in Gemology

Zircon is a fascinating gemstone with a long history of use in the field of gemology. Its unique properties and characteristics make it a sought-after gemstone for collectors and jewelry enthusiasts. Here’s a closer look at zircon in gemology:

Physical Characteristics:

Color: Zircon occurs in a wide range of colors, including blue, yellow, green, brown, red, and colorless. Among these, blue and red zircons are particularly popular in gemstone jewelry. Blue zircon, in particular, can resemble blue topaz and is often used as a more affordable alternative.

Luster: Zircon exhibits a high refractive index and excellent luster when cut and polished. It has a brilliant and sparkling appearance when used in jewelry, making it highly desirable.

Dispersion: Zircon is known for its strong dispersion, which is the ability to split white light into its spectral colors. This property gives zircon a remarkable “fire” or play of colors, making it even more appealing in jewelry.

Hardness: With a hardness rating of approximately 7.5 on the Mohs scale, zircon is durable enough for use in jewelry but should be handled with care to avoid scratching.

Gemological Classification: Zircon is classified as a nesosilicate mineral and is composed of zirconium silicate (ZrSiO4). It is distinct from cubic zirconia (CZ), a synthetic material often used as a diamond simulant, as they have different chemical compositions and physical properties.

Gemstone Varieties:

Blue Zircon: Blue zircon is one of the most popular varieties. It can exhibit vivid and vibrant blue colors, often resembling aquamarine or blue topaz. Heat treatment is commonly used to enhance the blue color of zircon.

Red Zircon: Red zircon is prized for its rich, deep red hues. These red zircons are often marketed as “hyacinth” or “jacinth” and can resemble precious red gemstones like ruby or spinel.

Yellow and Golden Zircon: These varieties range from pale yellow to golden hues and are appreciated for their warm and inviting colors. They can resemble yellow sapphire or yellow diamond.

Treatments: Heat treatment is a common practice in the gemstone industry to improve the color of zircon. This treatment can intensify or alter the gem’s color, making it more attractive to consumers. While heat-treated zircon is widely accepted, disclosure of treatment is essential in gem sales to maintain transparency and consumer confidence.

Care and Handling: Zircon is a durable gemstone for everyday wear in jewelry but should be protected from harsh chemicals and abrasive materials. To maintain its brilliance, zircon jewelry should be cleaned with mild soap, water, and a soft brush, and it should be stored separately to prevent scratching.

In summary, zircon is a versatile and captivating gemstone valued for its wide range of colors, strong dispersion, and luster. Whether used as a centerpiece in a jewelry setting or as an accent stone, zircon has a unique charm that appeals to gem collectors and those seeking distinctive and vibrant gemstone jewelry.

Industrial Applications

Zircon, a versatile mineral, finds a wide range of industrial applications owing to its unique properties. Here are some of the key industrial uses of zircon:

1. Refractory Materials: Zircon’s high melting point and resistance to heat make it a valuable component in refractory materials, such as zirconia refractories. These materials are used in the lining of furnaces, kilns, and crucibles in industries like metallurgy, ceramics, and glass manufacturing, where high temperatures are involved.

2. Ceramic and Tile Production: Zircon is used in the production of ceramic and tile materials, where it acts as an opacifier. It enhances the whiteness, opacity, and brightness of ceramic glazes and tiles, making them more visually appealing.

3. Foundry Casting: Zircon is utilized in the foundry industry as a molding material. Zircon sand is used to create molds for casting metals and alloys because it can withstand the high temperatures and thermal shocks encountered during the casting process.

4. Investment Casting: In the aerospace and automotive industries, zircon-based investment casting materials are used to create intricate and precise metal parts. The high refractoriness of zircon helps maintain the shape and detail of castings.

5. Nuclear Industry: Zirconium, derived from zircon, is crucial in the nuclear industry. Zirconium alloys are used in nuclear reactor components, such as fuel rods and cladding, due to their excellent resistance to corrosion and thermal neutron absorption.

6. Electronics and Optics: Zirconia (zirconium dioxide) is used in electronics as a ceramic insulator and in optical components for its high refractive index and transparency in the infrared spectrum. It’s used in items like oxygen sensors, solid oxide fuel cells, and high-quality camera lenses.

7. Dental Ceramics: Zirconia ceramics are widely used in dentistry for dental crowns, bridges, and dental implants. These ceramics are biocompatible, durable, and aesthetically pleasing.

8. Aerospace Components: Zirconium alloys and zirconia are used in aerospace components due to their heat resistance, high strength-to-weight ratio, and ability to withstand extreme conditions.

9. Chemical Processing: Zirconium compounds are employed in chemical processing industries as catalysts and corrosion-resistant materials, especially in applications where strong acids or aggressive chemicals are involved.

10. Grinding and Polishing: Zirconium-based abrasives are used for grinding and polishing hard materials like metals and ceramics. Zirconium oxide abrasives are known for their toughness and long-lasting abrasive qualities.

11. Pigments and Paints: Zircon compounds are used as pigments in paints and coatings. Zirconium silicate pigments provide opacity and brightness to paints and are commonly used in white and colored paints.

12. Oil and Gas Industry: Zirconium alloys are utilized in equipment and tools used in the oil and gas industry, where resistance to corrosion and high temperatures is essential.

In summary, zircon’s unique combination of high melting point, heat resistance, chemical inertness, and durability makes it valuable in various industrial applications. It plays a vital role in sectors such as ceramics, foundry casting, aerospace, nuclear technology, and many more, contributing to the development of advanced materials and technologies across industries.

Analytical Techniques

Analyzing and characterizing zircon and zircon-containing materials require various analytical techniques to assess their physical, chemical, and structural properties. Here are some common analytical techniques used in the study of zircon:

1. X-ray Diffraction (XRD): XRD is used to determine the crystal structure of zircon and identify its mineral phases. It can provide information about the crystal lattice parameters, unit cell dimensions, and crystal symmetry. XRD is essential for mineral identification and quantifying zircon content in geological samples.

2. Scanning Electron Microscopy (SEM): SEM allows for high-resolution imaging of zircon grains and surfaces. It provides detailed information about the morphology, size, and surface features of zircon crystals. Energy-dispersive X-ray spectroscopy (EDS) can be coupled with SEM to determine the elemental composition of zircon.

3. Electron Probe Microanalysis (EPMA): EPMA is used to quantitatively analyze the chemical composition of zircon at the microscale. It provides precise data on the concentration of various elements within zircon crystals, including trace elements such as uranium and thorium, which are crucial for radiometric dating.

4. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS): LA-ICP-MS is a powerful technique for analyzing trace element concentrations within zircon crystals. It is commonly used for geochronology studies, as it can determine the age of zircon crystals by measuring the isotopic ratios of elements like uranium and lead.

5. Electron Backscatter Diffraction (EBSD): EBSD is used to study the crystallography and orientation of zircon grains. It provides information about grain boundaries, crystallographic defects, and the distribution of crystallographic orientations within a sample.

6. Transmission Electron Microscopy (TEM): TEM allows for the examination of the internal structure and defects within zircon crystals at the nanoscale. It can reveal information about dislocations, inclusions, and microtextures.

7. Raman Spectroscopy: Raman spectroscopy is used to identify and characterize the mineral phases and crystal structure of zircon by measuring the vibrations of its atomic bonds. It can also detect impurities and defects within zircon crystals.

8. Fourier-Transform Infrared Spectroscopy (FTIR): FTIR spectroscopy is used to analyze the chemical composition and structural properties of zircon by measuring its infrared absorption and vibrational modes. It is particularly useful for identifying specific mineral phases and defects in zircon.

9. X-ray Fluorescence (XRF): XRF is used for bulk chemical analysis of zircon-containing materials. It provides information about the elemental composition of zircon samples and can detect major and trace elements.

10. Thermochemical Analysis: Techniques like thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) can be used to study the thermal behavior of zircon, including its decomposition, phase transitions, and thermal stability.

11. Nuclear Magnetic Resonance (NMR): NMR spectroscopy can provide information about the local atomic structure and chemical bonding in zircon. It is particularly useful for understanding the coordination environment of elements within the crystal lattice.

These analytical techniques, either individually or in combination, play a crucial role in studying zircon in various scientific disciplines, including geology, materials science, mineralogy, and gemology, and are essential for understanding its physical, chemical, and structural properties.

Locations of major Zircon deposits worldwide

Major zircon deposits are found in various parts of the world, with notable concentrations in specific regions. Here are some of the locations of major zircon deposits worldwide:

1. Australia: Australia is one of the world’s largest producers of zircon. The significant zircon deposits are primarily located in Western Australia, particularly in the Eneabba and Mindarie regions. Other Australian states, such as New South Wales and Queensland, also have zircon deposits.

2. South Africa: South Africa is known for its rich heavy mineral sands, which contain significant zircon deposits. The Western Cape, KwaZulu-Natal, and Eastern Cape provinces are key zircon-producing areas.

3. United States: Zircon deposits can be found in several U.S. states. Notable locations include the states of North Carolina, Florida, and Colorado. These deposits are often associated with heavy mineral sands along coastal areas.

4. India: India has zircon-bearing sands along its eastern and southern coasts, particularly in the states of Odisha, Tamil Nadu, and Kerala. These deposits contribute to India’s zircon production.

5. Brazil: Brazil is known for producing gem-quality zircons, especially from pegmatite deposits in Minas Gerais and Bahia states. These zircons are sought after for use in jewelry.

6. Madagascar: Madagascar has rich alluvial deposits of gem-quality zircons. The Andilamena and Ilakaka regions are known for producing colorful zircon gemstones.

7. Sri Lanka: Sri Lanka has a history of producing blue and green zircon gemstones from gem-bearing gravel beds and alluvial deposits.

8. Russia: Russia has zircon deposits in various regions, including the Ural Mountains and the Kola Peninsula. These deposits are a source of zirconium minerals.

9. Mozambique: The coastal regions of Mozambique, particularly the Chibuto and Inhambane areas, have significant deposits of heavy minerals, including zircon.

10. China: China also produces zircon from various locations, including coastal areas with heavy mineral sands and inland regions with zircon-bearing rocks.

These are some of the major zircon-producing regions around the world. The presence and significance of zircon deposits can vary within each country and region, and they are often associated with other valuable heavy minerals like ilmenite, rutile, and garnet in placer deposits or in igneous and metamorphic rocks.

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zircon

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zircon, silicate mineral, zirconium silicate, ZrSiO4, the principal source of zirconium. Zircon is widespread as an accessory mineral in felsic igneous rocks. It also occurs in metamorphic rocks and, fairly often, in detrital deposits. It occurs in beach sands in many parts of the world, particularly Australia, India, Brazil, and Florida, and is a common heavy mineral in sedimentary rocks. Gem varieties occur in stream gravels and detrital deposits, particularly in mainland Southeast Asia and Sri Lanka but also in Australia and New Zealand. Zircon forms an important part of the syenite of southern Norway and occurs in large crystals in Quebec. For detailed physical properties, see silicate mineral (table).

Learn how the earth keeps itself fresh and new and how the chemical properties of zircon determine the age of the earthThe chemical properties of zircon make it a useful tool in determining the age of Earth.(more)See all videos for this articleThe high refractive index and dispersion of zircon cause it to approach diamond in fire and brilliancy. Several varietal names have been applied to coloured gems. Hyacinth (jacinth) includes the clear, transparent red, orange, and yellow varieties. Matura diamond, from Sri Lanka, is clear and colourless, either naturally or made so through heat treatment under oxidizing conditions. The name jargon, like zircon derived from Persian zargūn, applies to all other colours. A lovely blue stone may be made by heat treatment under reducing conditions.

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Zircon: The gemstone Zircon information and pictures

Zircon: The gemstone Zircon information and pictures

 

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The Gemstone Zircon

Zircon is an important gemstone of many colors, and is an historical gemstone used for thousands of years. It is sometimes looked upon as a cheap Diamond simulant, but in actuality it can be a valuable gem. Its color diversity is caused by traces of certain impurities, some of which are radioactive. Zircon gemstones containing radioactive element traces undergo a process called metamiction, in which their inner crystal structure becomes destroyed. These radioactive forms of Zircon must be heated to stabilize them for use as gems. In fact, many of the gem forms of zircon (even those that are not radioactive) are heat treated to enhance color and increase transparency. The radioactivity in Zircon gemstones is very minimal and is generally believed to be safe, without posing any health hazards.

Chemical Formula

ZrSiO4

Color

White, Colorless, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray

Hardness

7.5

Crystal System

Tetragonal

Refractive Index

1.930 - 1.987

SG

4.6 - 4.8

Transparency

Transparent

Double Refraction

.059

Luster

Adamantine

Cleavage

3,2

Mineral Class

Zircon

Zircon AUCTIONS

ALL ABOUT

Zircon comes closer to resembling Diamond than any other natural gem. Its strong luster and intense fire gives it a real sparkle that is comparable to Diamond. However, its popularity is somewhat diminished by the fact that it is often perceived as an inexpensive Diamond imitation. Colorless Zircon is easily distinguished from Diamond by its strong double refraction and lower hardness.

The brilliant luster and fire of Zircon, combined with its good hardness and range of colors, make it a most desirable gem. However, it does have some undesirable traits. An interesting and strange habit exhibited in only few Zircons is that their color darkens and their luster dulls upon prolonged exposure to sunlight. This effect can be reversed by giving the stones a second heat treatment. Zircon is also prone to cracking and chipping if banged too hard. For this reason, care must also be taken when faceting Zircon gemstones. Another important factor when faceting Zircon is to minimize the appearance of its strong double refraction by cutting along proper angles. Zircons that are not faceted propely can appear blurry, due to strong double refraction.Zircon is sometimes confused with Cubic Zirconia. Cubic Zirconia, a synthetic, inexpensive Diamond simulant, resembles colorless Zircon and has a similar sounding name. However, the two are entirely separate substances, and have no connection with each other except for the fact that they both contain the element zirconium in their chemical structure.

USES

Zircon of all colors are used as gems, but blue, golden-brown, and white are the colors most often used. Blue Zircon, the most popular color, has a lively pastel blue, and occasionally has a very desirable striking bright blue color. Colorless Zircon is usually cut with a brilliant cut to bring out its fire to its fullest capability. It is often used as a cheaper, yet natural alternative to Diamond. The other color forms (yellow, green, pink, and purple) are less often seen in jewelry.Zircon is the traditional birthstone for December.

VARIETIES

Jacinth

 -   Yellow, orange, brown, or red variety of Zircon. Also synonymous with Hyacinth. Though the terms Jacinth and Hyacinth are no longer used in the gem trade, they are historically important names going back to biblical times. In ancient times, before there were mineralogical classifications for gemstones, the term Hyacinth may also have referred to an orange or brownish Topaz.

Jargon

 -  Colorless, pale gray, or pale yellow variety of Zircon.

Matura Diamond

 -   Trade name for colorless Zircon.

Starlite

 -  Blue gem variety of Zircon. The color of Starlite is rarely natural, and is almost always heat treated.

Zircon TREATMENTS AND ENHANCEMENTS

Zircon gemstones are often heat treated to produce good coloring and increase transparency. Heating semi-transparent, grayish-brown or reddish-brown Zircon from

most localities in an oxygen-free environment will give it a blue color.

If these blue stones are then re-heated in air, their color turns

golden-brown. Heat treatment of certain Zircon gemstones also produces

colorless gems. Almost all blue and colorless forms of Zircon are heat treated.

Zircon SOURCES

Zircon sources include Cambodia, Burma (Myanmar), Sri Lanka (Ceylon), Australia, Tanzania, Mozambique, Madagascar, Nigeria, Pakistan, and Afghanistan.

SIMILAR GEMSTONES

Because Zircon occurs in so many colors, there are many gemstones that resemble it.Colorless Zircon resembles Diamond. It also resembles synthetic Diamond simulants such as Cubic Zirconia and Strontium Titanate. It is distinguished from these and other colorless gem forms by its strong double refraction.Blue Zircon can be similar to Aquamarine, Blue Topaz, Blue Tourmaline, and Blue Spinel; Golden-brown Zircon can be similar to Topaz, Citrine, and Sapphire; Yellow zircon can be similar to Yellow Diamond, Yellow Sapphire, Golden Beryl, Chrysoberyl, and Topaz; and Pink Zircon can be similar to Rose Quartz, Morganite, Kunzite, Spinel, and Pink Topaz.The luster, fire, and double refraction make Zircon gemstones distinguishable from most others.

Zircon PHOTOS

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Zircon IN THE ROUGH PHOTOS

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The mineral Zircon

 

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Understanding Zircon: A Misunderstood Gemstone With Amazing Properties | Gem-A

Understanding Zircon: A Misunderstood Gemstone With Amazing Properties | Gem-A

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Understanding Zircon: A Misunderstood Gemstone with Amazing Properties

Gem-A

September 23, 2022

Zircon is one of the world’s most misunderstood gemstones. Regularly confused with and/or mistakenly linked to man-made cubic zirconia, it is a gemstone many people should learn more about. Gem-A Gemmology Tutor, Pat Daly, explains what makes zircon gemstones so special and explores the properties that make this underappreciated gemstone a great choice for jewellery. 

The Difference Between Zircon and Cubic Zirconia

Zircon seems to have suffered the fate that was once reserved for spinel. At one time, a few decades ago, synthetic spinel was one of the commonest artificial materials seen in cheap jewellery, and few consumers had heard of the natural stone. 

As a result, spinel became associated with factory-made material. Cubic zirconia is one of the commonest artificial products in today’s jewellery trade, and the reputation of zircon suffers because of the similarity between the two names.

Zircon and cubic zirconia are different stones which resemble each other only superficially. Zirconium is a metal which is a part of the chemical composition of both stones, but, in all other important ways, they are completely different materials. Gem zircon is a natural stone which has not been made synthetically. Cubic zirconia is an artificial product which never occurs in nature.

Rough cubic zirconia before cutting and faceting photographed by Pat Daly.

Lustre and Brilliance of Zircon

Zircon is a reasonably hard and tough stone with a bright lustre and good brilliance, which may be found in almost any colour. Lustre and brilliance depend on the ability to reflect light from the surface and from inside a stone. Most gem zircons are transparent and have few inclusions which can disturb the passage of light through them, and this improves their bright appearance. 

Fire in Zircon

Fire is the ability of a transparent, faceted stone to split white light into the colours of the spectrum so that, when they are illuminated by a spotlight, flashes of spectral colours are seen as the stone is moved. Few natural gems display this feature to a marked degree, but the fire in zircon comes close to that of a diamond. 

Where Are Zircons Found?

The most popular zircons in European and American jewellery are transparent, blue, white and golden-yellow stones, usually cut in the brilliant style to show their optical effects and colours to their best advantage. 

An example of a bright blue zircon gemstone photographed by Henry Mesa.

Most of these stones originate in Cambodia and are brown when they are mined. Heat treatment turns some of them blue, others white or yellow. Other colours of zircon include brown to green, yellow, orange, red and purple. All of them benefit from the brilliance of the material, which adds visual interest and makes them eye-catching. At present, these colours are seen less commonly in formal styles of jewellery, but they are seen in multi-stone necklaces and bracelets from Sri Lanka, for example. 

The main, though not the only, sources of gem quality zircon are Cambodia, Thailand, Myanmar and Sri Lanka. The stone has been used for hundreds to thousands of years, though its history is not well known because there are few records of gemstones from these times and the identities of the stones mentioned are not always certain. 

Since Sri Lanka is a major source of gems, however, and sapphires from this country are thought to have been exported to Europe and China more than 2000 years ago, it is probable that zircons were traded too. 

Fire in Zircon

Fire is the ability of a transparent, faceted stone to split white light into the colours of the spectrum so that, when they are illuminated by a spotlight, flashes of spectral colours are seen as the stone is moved. Few natural gems display this feature to a marked degree, but the fire in zircon comes close to that of a diamond. 

Where Are Zircons Found?

The most popular zircons in European and American jewellery are transparent, blue, white and golden-yellow stones, usually cut in the brilliant style to show their optical effects and colours to their best advantage. 

How Old Is Zircon?

Although gem-quality stones are rare, the mineral zircon has a worldwide distribution, and crystals may be very old because the stone is durable and resistant to change. The oldest recorded zircons are about 4.4 billion years old, close to the age of Earth itself. They have been found in Australia, as detrital grains, not of gem quality, in a sedimentary rock which was formed after the erosion of the one in which the zircon grew. Gem zircons are not so old. Some of those from Sri Lanka have been dated at about 500 million years, and some Cambodian stones to about 1 million years. 

A fine zircon gemstone (left) next to a dark coloured sapphire from the Gem-A Archives.

Zircon can be dated with confidence because, when it grows, it incorporates small amounts of uranium. Over time, this breaks down into other chemical elements, including lead. The proportions of the trace elements present in the stone enable scientists to establish ages for zircon crystals and for zircon inclusions in rocks and minerals. For example, this has been used in gemmology to distinguish sapphires from Kashmir, containing zircons less than 50 million years old, from stones from Madagascar, which resemble them closely, but whose inclusions give dates several hundred million years older.

The radioactive impurities in zircon break down over time, emitting heavy atomic particles which disrupt the regular arrangement of atoms in the crystal. Over millions of years, the structure may be broken down partly or completely, changing the properties of the material. Gemmologists must take such variations into account when identifying zircons. 

Refractive Index of Zircon 

Zircon is distinctive because few stones have such a bright appearance. Many gemstones share the property of dividing light into two parts so that doubled images of, for example, facet edges on the pavilion may be seen through the crown of the stone (see the main article image). 

A group of multi-coloured zircon gemstones from the Gem-A Archives.

In most stones, however, the property is hard to see without careful inspection. This is not the case with zircon, in which it may be noticed, in large stones, with the unaided eye. In stones which have suffered a breakdown of the crystal structure, which are called low zircons, this property may be reduced or eliminated, and this is one of the factors which must be considered by a gemmologist. 

The optical properties of zircon cannot be measured with a refractometer, one of the main gemmological instruments, but most stones can be identified with a spectroscope. This instrument splits light into the colours of the spectrum, parts of which may be absorbed from light passing through a stone, creating a pattern of shadows against a ribbon of coloured light. The pattern of shadows produced by most zircons is variable but easily recognised, especially because there is a line or band in the red, in low zircons, as well as in others. 

A very few rare, mostly brown, collectors’ stones show a pattern resembling it, and some zircons do not show a spectrum. These exceptions must be dealt with by additional tests, but it is found that most zircons are fairly easy to identify.

A rough zircon crystal from the Gem-A Archives.

Hardness of Zircon

Most zircon has a hardness which is in the same range as quartz gems, garnets, emeralds and others. These stones may be scratched by contact with sapphires, rubies and diamonds and should not be allowed to rub against them when jewellery is stored after use. They may also be scratched by industrial and some household abrasives. Low zircons have a lesser hardness, similar to tanzanite and peridot, and deserve to be treated more gently.

Heat Treated Zircon

Zircons, especially heat-treated stones, are brittle and will become chipped along facet edges if they are not worn and handled carefully. 

Zircons are resistant to chemical changes, but some heat-treated stones may discolour if exposed to ultraviolet, so they should not be left for long periods in sunlight. When testing zircons, it is unwise to expose them to short-wave ultraviolet radiation, which may induce an unwanted yellowish colour (this tends to fade when the stone is kept in the dark, but it may take days or weeks to happen).

Surface markings on a zircon crystal under the microscope from the Gem-A Archives.

In conclusion, zircon is a beautiful coloured stone which is available in relatively large sizes at a cost that is moderate when compared with some better-known stones. It is suitable for all kinds of jewellery and, provided that it is treated with reasonable care, it will survive a lifetime’s wear in good condition.

Improve your knowledge of zircon by studying gemmology here at the Gemmological Association of Great Britain (Gem-A). Discover our online-only beginner’s gemmology course, GemIntro, and get started today. 

Main image: Zircon doubling under the microscope photographed by Pat Daly.

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Gemstone Information A-Z

Zircon Info

By Gavin Clarke

Reviewed By Thomas Dahlberg

What can I find in this article?

Zircon Colors

Zircon Varieties

Zircon Clarity

Zircon Meaning

Healing benefits of Zircon

Zircon Prices

Where are zircons found?

Can Zircon be treated?

What jewelry is Zircon suitable for?

Did you know? Interesting facts about zircon

How to care for Zircon

How can you tell a real Zircon?

Zircon - Gemological Properties

Can Zircon change color?

How can you tell a good quality zircon?

Zircon Gemstone Information

Natural Zircon Gemstones

Zircon is an historic crystal both in terms of man and the earth itself. A piece of zircon found in Australia in 2014 has been dated back nearly 4.5 billion years making it virtually as old as the planet itself. Named hyacinth or jacinth in the bible, a variety of zircon was one of the 12 stones of Israel mentioned in the bible and a legendary tree ripe with zircon gems is mentioned in traditional Hindu poem.

Zircon's image has suffered over the years first by its use in its clear form as a cheaper substitute for diamonds and then more recently by getting confused with the man-made diamond substitute, cubic zirconium. This is a shame because the zircon crystals make a beautiful gem covering an array of colors from golden yellows to deep reds, greens and blues and even black.

Zircon's name comes from the Arabic 'Zarqun' meaning red or the 'similar sounding Persian word 'Zargun' meaning golden and it is found across the world with east Africa and south east Asia producing some of the finest examples. It was renamed Zircon in 1783 by Abraham Werner.

Zircon Colors

Which colors of zircon are the most expensive? Zircons come in many colors, including some stunning yellow and orange varieties, even pinks and greens, but undoubtedly the favorite and most valuable are the attractive blue examples. Although they may be the most popular, blue zircons are nearly always naturally brown and are turned into stunning blues through heat treatment.

The color of Zircon gemstones can change dramatically when viewed from different angles, for example blue zircon can look greenish from certain angles. The technical term for this is pleochroism. Medium dark, pure blue stones have the most value. Green zircons are probably the rarest color zircon, they are very hard to find and typically very expensive. White zircon, which is in reality clear, is wanted for its resemblance to diamonds.

Zircon Varieties

The mineral zircon is present throughout the world in such abundance that it could be thought of as ubiquitous and is so small that it is barely noticed. Zircon is so resilient that it can survive in soil, rocks and sediments for billions of years, the entire lifespan of our planet. In certain circumstances larger crystals can form and these crystals are sometimes of extremely high clarity. Zircon is the encompassing name but its assortment of colors produced by traces of impurities has lead to a number of alternative names including:

Canary Zircon yellow in color just like the bird

Chocolate Zircon brown in color

Ratanakari Zircon a blue stone named after the Cambodian mine where it is excavated

Mashewa Zircon an orange variety from the Mashewa mine in Tanzania

Hyacinth from yellow to garnet

Jargoon a pale almost colorless yellow gem

Zircon is so resilient that it can survive in soil, rocks and sediments for billions of years, the entire lifespan of our planet.

Zircon gemstones are considered to have high levels of clarity, most gemstones for sale are what we would call 'eye clean', that is any impurities or flaws (known as inclusions) are invisible to the naked eye. As it is a natural gemstone such inclusions certainly exist but would only be visible under magnification. Most valuable Zircon gemstones are transparent or translucent and have a sparkle or a characteristic 'fire' that distinguish them from most other gemstones. This distinctive 'sparkle' is known as dispersion and can be measured using a refractometer.

Zircon Clarity

Zircon gemstones are considered to have high levels of clarity, most gemstones for sales are what we would call 'eye clean', that is any impurities or flaws (known as inclusions) are invisible to the naked eye. As it is a natural gemstone such inclusions certainly exist but would only be visible under magnification. Most valuable Zircon gemstones are transparent or translucent and have a sparkle or a characteristic 'fire' that distinguish them from other gemstones.

Zircon Meaning

As one of the oldest minerals on earth, Zircon has a unique spirituality about it. In the Middle Ages, Zircon was said to aid in resting and sleeping warding off nightmares and bringing prosperity, honor and wisdom to its owner. Zircon will enable you to deal with feelings of loss whether it is a family member, friend or beloved pet. It can boost your passion for life or work. Zircon is an excellent meditation gemstone. Zircon can be a good gift for your child if you wish you connect with him or her. The different color zircons can have different spiritual effects, for example the Blue Zircon stone can help your relationships and build self confidence while the colorless variety or Matura Diamond (a misleading name for a clear zircon) is great for mental purification.

Healing benefits of Zircon

Zircon has been recommended for centuries to alleviate a range of ailments, soothing pains, relieve stomach cramps, asthma, lung problems and some forms of cardiac arrhythmia. Some believe it can aid with menstrual pains and act as a sexual stimulant.

Zircon is very slightly radioactive so some care should be taken when wearing it but please note that the levels of radioactivity in zircon pose no threat when worn as jewelry.

Disclaimer: Metaphysical and Alternative Crystal Healing Powers and Properties are not to be taken as confirmed advice. Traditional, Ceremonial and Mythological Gemstone Lore is collected from various resources and does not represent the sole opinion of SETT Co., Ltd. This information is not to replace the advice of your doctor. Should you have any medical conditions, please see a licensed medical practitioner. GemSelect does not guarantee any claims or statements of healing or astrological birthstone powers and cannot be held liable under any circumstances.

Zircon Prices

The 4 Cs, color, clarity, cut and carat, largely determine the price of a gemstone and this is no different for a zircon. The colorless or white zircon resembles the diamond and is in fact rarer than a diamond but cannot command a similar price. Zircon can cost around $50 to $400 per carat depending on the above mentioned 4 Cs. The most popular zircon is the blue variety produced by heat treatment of brown zircon usually from Myanmar or Cambodia, and usually commands a good fee. Green zircon is the rarest color and can also reach a significant price. The origin of the zircon stone can also affect the price with Sri Lanka and Cambodia providing premium priced clear stones and Cambodia also being the source of the finest blue varieties.

Zircon Price List

Color

Weight range

Price range / USD

Blue

1 - 2ct

$15 - $50/ct

Blue

2 - 5ct

$35 - $180/ct

Blue

5ct +

$70 - $350/ct

White

1 - 2ct

$15 - $80/ct

White

2 - 5ct

$18 - $40/ct

White

5ct +

$40 - $80/ct

Fancy

1 - 2ct

$15 - $100/ct

Fancy

2 - 5ct

$20 - $250/ct

Fancy

5ct +

$40 - $400/ct

Where are zircons found?

Zircons in some form or another are found on all continents including Antarctica but larger Gem quality zircon crystals have been produced from alluvial deposits in Sri Lanka, Cambodia, Myanmar, and Vietnam for hundreds of years. More recently gem-grade deposits have been mined in Australia, South America, Nigeria, Madagascar and wherever pegmatite rock can be found.

Can Zircon be treated?

Many zircon stones are completely untreated, however to get the very popular and beautiful Blue zircon or brilliant White zircon, the original gemstones have to be heat treated. Some colors are unenhanced, including rose and rose-orange zircon from Tanzania, and orange to orange-brown zircon from Cambodia. Green zircon is very rare and owes its color to minute natural traces of uranium and thorium but is sometimes heated to lighten their coloring. Golden-yellow zircon is occasionally heated. Certain stones can be heat treated twice, once in an oxygen free environment to turn blue, then re-heated in air to produce golden brown gems. It should be noted that some treated gemstones have been known to fade in sunlight or under ultra-violet light.

What jewelry is Zircon suitable for?

Zircon has a reading of 7 to 7.5 on the Mohs scale for gem quality stones, meaning they are strong enough the withstand the rigors of daily wear if fashioned into rings, pendants, bracelets or necklaces although care should be taken to avoid any sharp blows. Zircon can be brittle so should be stored carefully to avoid contact with hard materials which could break, chip or scratch the gem.To learn more about the Mohs scale please see our article here.

The wide range of beautiful and interesting colors as well as their renowned sparkle or 'fire' make Zircons much sought after as jewelry. To maximize the effects of this very high luster zircons are usually fashioned into round or oval shapes with a brilliant or step cut. Zircons color and luster is so attractive that it looks stunning when set in finished jewelry designs and because of the variety of hues available, the stone can set in silver, gold, white gold or any medium you prefer.

White zircon is a go-to diamond substitute for those wanting a gemstone with diamond-like luster but who don't wish to pay the high price of a real diamond.

Most zircon stones are small in size, due to their dense nature, but some rare large stones can be found. Larger stones are excellent for bold designs, such as unique pendants or brooches. Buy colored gemstones by size and not by carat weight - a 6mm round stone will be 6mm but the very dense zircon could be smaller than its carat weight may suggest. For example, Zircon is about 50% denser than diamond - if the diamond weighs 1 carat, the same size zircon will weigh about 1.5 carats.

Did you know? Interesting facts about zircon

Zircons are one of three birthstones for the month of December.

White zircon is the gemstone of the planet Venus and is believed to bring good fortune to those born under the sign of Taurus and Libra.

Zircon can contain small traces of uranium, leading it to change properties by irradiating itself!

Tiffany's world famous gem buyer, George Kunz was a great fan of Blue Zircon and wanted to rename it 'Starlite' to emphasize the gem's brilliant luster. It did not catch on.

Zircon has double refraction, light entering the gem splits into to two rays of light, giving it its well known sparkle.

Zircons are so durable and resistant to chemical attack that they never disappear.

It is believed that zircons were formed by crystallization within volcanic rock but new theories suggest zircons could have been created when meteors hit earth billions of years ago.

Layers of additional zircon grow around the original crystal like tree rings, these rings can record geologic events tracing the history of our planet.

Zircon is of such interest to geoscientists that it has spawned the discipline of "zirconology".

How to care for Zircon

While it is hard enough for most types of jewelry, Zircon still needs to be taken care of. It is best to store gems and jewelry separately from one another to prevent scratches and fractures. When storing zircon gemstones, it is a good idea to wrap them in a soft cloth or place them inside a fabric-lined box. Always remove jewelry when engaging in any type of physical activity, including household chores, exercise or sports. When not being worn, we recommend keeping your zircons out of direct sunlight and away from strong sources of heat as this could alter the coloring. Simply wipe down your zircon with a soft cloth or brush or wash with a mild soap or detergent if necessary and rinse with warm water. Avoid steamers or ultrasonic cleaners when cleaning zircon gems and jewelry.

How can you tell a real Zircon?

The only way to be sure of any gemstone's authenticity is through a professional lab test using refractive index tests or specific gravity tests. Identifying a zircon without one of these tests would be difficult. Because of its similarity to diamond, colorless faceted zircon has been used as a substitute, sometimes fraudulently. At GemSelect, we currently offer brief identification reports from your choice of two well-respected independent gemological laboratories, The Asian Institute of Gemological Sciences (AIGS) and Burapha Gemological Laboratory (BGL Lab).

Zircon - Gemological Properties

Chemical Formula:

ZrSiO4; Zirconium silicate

Crystal Structure:

(Tetragonal), short, stocky, four-sided prisms with pyramidal ends

Color:

Colorless, yellow, brown, orange, red violet, blue, green

Hardness:

6.5 to 7.5 on the Mohs scale

Refractive Index:

1.810 to 2.024

Density:

3.93 to 4.73

Cleavage:

Indistinct

Transparency:

Transparent to translucent

Double Refraction or Birefringence:

0.002 to 0.059

Luster:

Vitreous to brilliant sheen

Fluorescence:

Blue: very weak; light-orange, red and brown: weak, dark-yellow

Can Zircon change color?

We know that zircon can change color permanently when heated in laboratories but they can also change color in sunlight, in darkness or under incandescent light. Some examples are said to go from orange to colorless when left in the sun then slowly return to orange when kept in the dark. This phenomenon, peculiar to just a few gems, is called tenebrescence.

How can you tell a good quality zircon?

As with most gems, an appraisal of a gemstone's quality is based on the 4 Cs, color, clarity, cut and carat. With Zircons it is the color and cut that are the most important. Zircons are typically inclusion free and most gems look clear to the naked eye. We prefer to gauge a zircon by its physical size in millimeters rather than carats. This is because the zircon is a very dense gemstone, for example it is about 50% more dense than a diamond so a 2 or 3 carat zircon would look a lot smaller than a similar carat diamond. So on a zircon look for deep and saturated colors. Make sure the the gem facets are cut in the proper angles so it will not show any window effect and display its full fire.

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