Scheelite: Difference between revisions
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| solubility = Soluble in alkalis. Insoluble in acids | | solubility = Soluble in alkalis. Insoluble in acids | ||
| diaphaneity = Transparent to opaque | | diaphaneity = Transparent to opaque | ||
| other = Fluorescence under short-wave UV is bright blue, bluish white to yellow. Specimens with more molybdenum tend to fluoresce white to yellow, similar to powellite. Occasionally fluoresces red under mid-wave UV. | | other = Fluorescence under short-wave UV is bright blue, bluish white to yellow. Specimens with more molybdenum tend to fluoresce white to yellow, similar to powellite. Occasionally, it fluoresces red under mid-wave UV. | ||
| references = <ref name=Handbook>http://rruff.geo.arizona.edu/doclib/hom/scheelite.pdf Handbook of Mineralogy</ref><ref name=Mindat>http://www.mindat.org/min-3560.html Mindat.org</ref><ref name=Webmin>http://webmineral.com/data/Scheelite.shtml Webmineral data</ref><ref name=Klein>Klein, Cornelis and Cornelius S. Hurlbut, ''Manual of Mineralogy'', Wiley, 20th ed., 1985, p. 356 {{ISBN|0-471-80580-7}}.</ref> | | references = <ref name=Handbook>http://rruff.geo.arizona.edu/doclib/hom/scheelite.pdf Handbook of Mineralogy</ref><ref name=Mindat>http://www.mindat.org/min-3560.html Mindat.org</ref><ref name=Webmin>http://webmineral.com/data/Scheelite.shtml Webmineral data</ref><ref name=Klein>Klein, Cornelis and Cornelius S. Hurlbut, ''Manual of Mineralogy'', Wiley, 20th ed., 1985, p. 356 {{ISBN|0-471-80580-7}}.</ref> | ||
}} | }} | ||
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== Properties == | == Properties == | ||
[[File:CaWO4.tif|thumb|left|Structure of CaWO<sub>4</sub><ref>{{cite journal | last1 = Zalkin | first1 = A. | last2 = Templeton | first2 = D.H. | year = 1964 | title = X-ray diffraction refinement of the calcium tungstate structure | doi = 10.1063/1.1725143 | journal = Journal of Chemical Physics | volume = 40 | issue = 2| pages = 501–504 | bibcode = 1964JChPh..40..501Z | url = https://cloudfront.escholarship.org/dist/prd/content/qt7mp8m04j/qt7mp8m04j.pdf }}</ref>]] | [[File:CaWO4.tif|thumb|left|Structure of CaWO<sub>4</sub><ref>{{cite journal | last1 = Zalkin | first1 = A. | last2 = Templeton | first2 = D.H. | year = 1964 | title = X-ray diffraction refinement of the calcium tungstate structure | doi = 10.1063/1.1725143 | journal = Journal of Chemical Physics | volume = 40 | issue = 2| pages = 501–504 | bibcode = 1964JChPh..40..501Z | url = https://cloudfront.escholarship.org/dist/prd/content/qt7mp8m04j/qt7mp8m04j.pdf }}</ref>]] | ||
Its crystals are in the [[tetragonal]] [[crystal system]], appearing as dipyramidal pseudo-octahedra. Colors include golden yellow, brownish green to dark brown, pinkish to reddish gray, orange and colorless. Transparency ranges from translucent to transparent and crystal faces are highly [[Lustre (mineralogy)|lustrous]] (vitreous to adamantine). Scheelite possesses distinct [[Cleavage (crystal)|cleavage]] and its fracture may be [[conchoidal fracture|subconchoidal]] to uneven. Its [[specific gravity]] is high at 5.9–6.1 and its [[Mohs scale of hardness|hardness]] is low at 4.5–5.<ref name=Handbook/> Aside from pseudo-octahedra, scheelite may be columnar, granular, tabular or massive in [[crystal habit|habit]]. [[Druse (geology)|Druzes]] are | Its crystals are in the [[tetragonal]] [[crystal system]], appearing as dipyramidal pseudo-octahedra. Colors include golden yellow, brownish green to dark brown, pinkish to reddish gray, orange and colorless. Transparency ranges from translucent to transparent, and crystal faces are highly [[Lustre (mineralogy)|lustrous]] (vitreous to adamantine). Scheelite possesses distinct [[Cleavage (crystal)|cleavage]], and its fracture may be [[conchoidal fracture|subconchoidal]] to uneven. Its [[specific gravity]] is high at 5.9–6.1 and its [[Mohs scale of hardness|hardness]] is low at 4.5–5.<ref name=Handbook/> Aside from pseudo-octahedra, scheelite may be columnar, granular, tabular or massive in [[crystal habit|habit]]. [[Druse (geology)|Druzes]] are pretty rare and occur almost exclusively at Zinnwald, [[Czech Republic]]. [[Crystal twinning|Twinning]] is also commonly observed, and crystal faces may be striated. Scheelite has a white [[Mineral#Streak|mineral streak]] and is brittle. | ||
Gems cut from transparent material are fragile. Scheelite's [[refractive index]] (1.918–1.937 uniaxial positive, with a maximum [[birefringence]] of 0.016) and [[dispersion (optics)|dispersion]] (0.026) are both moderately high. These factors combine to result in scheelite's high lustre and perceptible "fire", approaching that of [[diamond]]. | Gems cut from transparent material are fragile. Scheelite's [[refractive index]] (1.918–1.937 uniaxial positive, with a maximum [[birefringence]] of 0.016) and [[dispersion (optics)|dispersion]] (0.026) are both moderately high. These factors combine to result in scheelite's high lustre and perceptible "fire", approaching that of [[diamond]]. | ||
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Scheelite occurs in [[Contact metamorphism|contact metamorphic]] [[skarn]]s; in high-temperature [[hydrothermal]] [[Vein (geology)|veins]] and [[greisen]]; less commonly in [[granite]] [[pegmatite]]s.<ref name=Handbook/> Temperature and pressure of formation is between {{convert|200 and 500|°C|sigfig=1}} and from {{Convert|200 to 1,500|bar|psi}}.<ref>Lindgren, W. (1933) ''Ore Deposits of the Western States,'' pp. 518, 535</ref> Typical mineral association includes [[cassiterite]], [[wolframite]], [[topaz]], [[fluorite]], [[apatite]], [[tourmaline]], [[quartz]], [[grossular]]–[[andradite]], [[diopside]], [[vesuvianite]] and [[tremolite]].<ref name=Handbook/> | Scheelite occurs in [[Contact metamorphism|contact metamorphic]] [[skarn]]s; in high-temperature [[hydrothermal]] [[Vein (geology)|veins]] and [[greisen]]; less commonly in [[granite]] [[pegmatite]]s.<ref name=Handbook/> Temperature and pressure of formation is between {{convert|200 and 500|°C|sigfig=1}} and from {{Convert|200 to 1,500|bar|psi}}.<ref>Lindgren, W. (1933) ''Ore Deposits of the Western States,'' pp. 518, 535</ref> Typical mineral association includes [[cassiterite]], [[wolframite]], [[topaz]], [[fluorite]], [[apatite]], [[tourmaline]], [[quartz]], [[grossular]]–[[andradite]], [[diopside]], [[vesuvianite]] and [[tremolite]].<ref name=Handbook/> | ||
Scheelite usually occurs in tin-bearing veins | Scheelite usually occurs in tin-bearing veins and is sometimes found in association with gold. Fine crystals have been obtained from Caldbeck Fells in [[Cumbria]], Zinnwald/Cínovec and [[Loket (Sokolov District)|Elbogen]] in [[Bohemia]], [[Guttannen]] in [[Switzerland]], the [[Giant Mountains]] in [[Silesia]], [[Dragoon Mountains]] in [[Arizona]] and elsewhere. At [[Trumbull, Connecticut|Trumbull in Connecticut]] and [[Mount Kimpu|Kimpu-san]] in Japan, large crystals of scheelite completely altered to wolframite have been found: those from Japan have been called “reinite.”<ref>{{Cite EB1911|wstitle=Scheelite}}</ref> It was mined until 1990 at [[King Island (Tasmania)|King Island]], Australia, [[Glenorchy, New Zealand|Glenorchy]] in [[Central Otago]] and [[Macraes Flat]] in [[North Otago]] and also at The Golden Bar mine at Dead Horse Creek during World War I in [[Nelson, New Zealand]]. There is a high concentration of scheelite in the Northeast of Brazil, mainly in the [[Currais Novos mine]] in Rio Grande do Norte State.<ref>Amstutz, Gerhard Christian et al. (Ed.). ''Ore Genesis: The State of the Art. Vol. 2''. Springer Science & Business Media, 2012, p. 418.</ref> One of the world's largest scheelite mining companies is in [[Luoyang]], China.<ref>{{Cite web|url=https://www.jiemian.com/article/5847842.html|title = 洛阳钼业去年净利增长25%，贡献最大的这两项业务|界面新闻}}</ref> | ||
== History == | == History == | ||
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== Synthetics == | == Synthetics == | ||
{{unreferenced section|date=April 2024}} | {{unreferenced section|date=April 2024}} | ||
Scheelite as a diamond imitation has been surpassed by more convincing products, like [[cubic zirconia]] and [[moissanite]] | Scheelite as a diamond imitation has been surpassed by more convincing products, like [[cubic zirconia]] and [[moissanite]]. Synthetic scheelite is occasionally offered as natural scheelite, and collectors may thus be fooled into paying high prices for it. [[Gemology|Gemologists]] distinguish natural scheelite from synthetic material mainly by microscopic examination: Natural material is very seldom without internal growth features and inclusions (imperfections), while synthetic material is usually spotless. Distinctly artificial curved striae and clouds of minute gas bubbles may also be observed in synthetic scheelite. | ||
The visible [[absorption spectrum]] of scheelite, as seen by a hand-held (direct-vision) [[spectroscope]], may also be of use: most natural stones show | The visible [[absorption spectrum]] of scheelite, as seen by a hand-held (direct-vision) [[spectroscope]], may also be of use: most natural stones show several faint absorption lines in the yellow region of the spectrum (~585 nm) due to [[praseodymium]] and [[neodymium]] trace impurities. Conversely, synthetic scheelite is often without such a spectrum. | ||
== Applications == | == Applications == | ||
Scheelite is widely used in | Scheelite is widely used in [[phosphor]]s,<ref>{{cite web |url=https://www.refractorymetal.org/uses-of-tungsten/ |title=3 Primary Uses of Tungsten |website=Advanced Refractory Metals |date=24 March 2020 |access-date=1 August 2024}}</ref> particularly in [[scintillator]]s for X-ray and gamma-ray detection.<ref>{{cite journal |last=Gillette |first=R.H. |year=1950 |title=Calcium and Cadmium Tungstate as Scintillation Counter Crystals for Gamma-Ray Detection |journal=Rev. Sci. Instrum. |volume=21 |issue=4 |pages=294–301 |doi=10.1063/1.1745567|bibcode=1950RScI...21..294G }}</ref> The second and third iterations of the [[Cryogenic Rare Event Search with Superconducting Thermometers]] dark matter detector experiment use calcium tungstate as a scintillator as well.<ref>{{cite journal|last1=Davis|first1=Jonathan|title=The Past and Future of Light Dark Matter Direct Detection|journal=Int. J. Mod. Phys. A|year=2015|volume=30|issue=15|page=1530038|doi=10.1142/S0217751X15300380|arxiv=1506.03924|bibcode=2015IJMPA..3030038D|s2cid=119269304}}</ref> It is also utilized in [[Fluorescence|fluorescent]] lighting systems for its ability to convert [[Ultraviolet|ultraviolet light]] into [[Light|visible light]].<ref>{{cite book |author=Oliver Caldwell Ralston |year=1944 |title=Fluorescent Minerals Used in Lighting and Elsewhere |publisher=U.S. Department of the Interior, Bureau of Mines |page=16 |asin=B003YKFVMU}}</ref> In some [[cathode-ray tube]]s (CRTs), calcium tungstate (scheelite) is used as a [[Phosphorescence|phosphorescent]] screen material.<ref>{{cite journal |last1=Bahmani |first1=Hadi |last2=Mostofinejad |first2=Davood |year=2022 |title=Microstructure of ultra-high-performance concrete (UHPC) – A review study |journal=Journal of Building Engineering |volume=50 |issue=1 |article-number=104118 |doi=10.1016/j.jobe.2022.104118}}</ref> | ||
== In popular culture == | == In popular culture == | ||
Scheelite figures in the manga series ''[[Dr. Stone]]'', as a precursor to tungsten, and for its fluorescence.<ref>{{Cite web|last=Gleeson|first=Kayla|date=7 December 2019|title=English Dub Review: Dr. STONE "Spartan Crafts Club"|url=https://www.bubbleblabber.com/english-dub-review-dr-stone-spartan-crafts-club/|access-date=26 January 2021|website=Bubbleblabber|language=en-US}}</ref> | Scheelite figures in the manga series ''[[Dr. Stone]]'', as a precursor to tungsten, and for its fluorescence.<ref>{{Cite web|last=Gleeson|first=Kayla|date=7 December 2019|title=English Dub Review: Dr. STONE "Spartan Crafts Club"|url=https://www.bubbleblabber.com/english-dub-review-dr-stone-spartan-crafts-club/|access-date=26 January 2021|website=Bubbleblabber|language=en-US}}</ref> | ||
==References== | == References == | ||
{{Reflist}} | {{Reflist}} | ||
==Further reading== | == Further reading == | ||
{{Wiktionary}} | {{Wiktionary}} | ||
{{Commons category|Scheelite}} | {{Commons category|Scheelite}} | ||
*Anderson, B. W., Jobbins, E. A. (Ed.) (1990). ''Gem testing''. Butterworth & Co Ltd, Great Britain. {{ISBN|0-408-02320-1}} | * Anderson, B. W., Jobbins, E. A. (Ed.) (1990). ''Gem testing''. Butterworth & Co Ltd, Great Britain. {{ISBN|0-408-02320-1}} | ||
{{Tungsten minerals}} | {{Tungsten minerals}} | ||
{{ | {{Ores}} | ||
{{Authority control}} | {{Authority control}} | ||
Latest revision as of 10:18, 14 December 2025
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Scheelite is a calcium tungstate mineral with the chemical formula CaWO4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist Carl Wilhelm Scheele (1742–1786). Well-formed crystals are sought by collectors and are occasionally fashioned into gemstones when suitably free of flaws. Scheelite has been synthesized using the Czochralski process; the material produced may be used to imitate diamond, as a scintillator, or as a solid-state lasing medium. It was also used in radium paint in the same fashion as was zinc sulphide, and Thomas Edison invented a fluoroscope with a calcium tungstate-coated screen, making the images six times brighter than those with barium platinocyanide; the latter chemical allowed Röntgen to discover X-rays in early November 1895. The semi-precious stone marketed as 'blue scheelite' is actually a rock type consisting mostly of calcite and dolomite, with occasional traces of yellow-orange scheelite.
Properties
Its crystals are in the tetragonal crystal system, appearing as dipyramidal pseudo-octahedra. Colors include golden yellow, brownish green to dark brown, pinkish to reddish gray, orange and colorless. Transparency ranges from translucent to transparent, and crystal faces are highly lustrous (vitreous to adamantine). Scheelite possesses distinct cleavage, and its fracture may be subconchoidal to uneven. Its specific gravity is high at 5.9–6.1 and its hardness is low at 4.5–5.[2] Aside from pseudo-octahedra, scheelite may be columnar, granular, tabular or massive in habit. Druzes are pretty rare and occur almost exclusively at Zinnwald, Czech Republic. Twinning is also commonly observed, and crystal faces may be striated. Scheelite has a white mineral streak and is brittle.
Gems cut from transparent material are fragile. Scheelite's refractive index (1.918–1.937 uniaxial positive, with a maximum birefringence of 0.016) and dispersion (0.026) are both moderately high. These factors combine to result in scheelite's high lustre and perceptible "fire", approaching that of diamond.
Scheelite fluoresces under shortwave ultraviolet light, the mineral glows a bright sky-blue. The presence of molybdenum trace impurities occasionally results in a green glow. Fluorescence of scheelite, sometimes associated with native gold, is used by geologists in the search for gold deposits.
Occurrence
Scheelite occurs in contact metamorphic skarns; in high-temperature hydrothermal veins and greisen; less commonly in granite pegmatites.[2] Temperature and pressure of formation is between Script error: No such module "convert". and from Script error: No such module "convert"..[3] Typical mineral association includes cassiterite, wolframite, topaz, fluorite, apatite, tourmaline, quartz, grossular–andradite, diopside, vesuvianite and tremolite.[2]
Scheelite usually occurs in tin-bearing veins and is sometimes found in association with gold. Fine crystals have been obtained from Caldbeck Fells in Cumbria, Zinnwald/Cínovec and Elbogen in Bohemia, Guttannen in Switzerland, the Giant Mountains in Silesia, Dragoon Mountains in Arizona and elsewhere. At Trumbull in Connecticut and Kimpu-san in Japan, large crystals of scheelite completely altered to wolframite have been found: those from Japan have been called “reinite.”[4] It was mined until 1990 at King Island, Australia, Glenorchy in Central Otago and Macraes Flat in North Otago and also at The Golden Bar mine at Dead Horse Creek during World War I in Nelson, New Zealand. There is a high concentration of scheelite in the Northeast of Brazil, mainly in the Currais Novos mine in Rio Grande do Norte State.[5] One of the world's largest scheelite mining companies is in Luoyang, China.[6]
History
Scheelite was first described in 1751 for an occurrence in Mount Bispbergs klack, Säter, Dalarna, Sweden, and named for Carl Wilhelm Scheele (1742–1786).[7] Owing to its unusual heaviness, it had been given the name tungsten by the Swedes, meaning “heavy stone.” The name was later used to describe the metal, while the ore itself was given the name scheelerz or scheelite.[8]
Synthetics
Script error: No such module "Unsubst". Scheelite as a diamond imitation has been surpassed by more convincing products, like cubic zirconia and moissanite. Synthetic scheelite is occasionally offered as natural scheelite, and collectors may thus be fooled into paying high prices for it. Gemologists distinguish natural scheelite from synthetic material mainly by microscopic examination: Natural material is very seldom without internal growth features and inclusions (imperfections), while synthetic material is usually spotless. Distinctly artificial curved striae and clouds of minute gas bubbles may also be observed in synthetic scheelite.
The visible absorption spectrum of scheelite, as seen by a hand-held (direct-vision) spectroscope, may also be of use: most natural stones show several faint absorption lines in the yellow region of the spectrum (~585 nm) due to praseodymium and neodymium trace impurities. Conversely, synthetic scheelite is often without such a spectrum.
Applications
Scheelite is widely used in phosphors,[9] particularly in scintillators for X-ray and gamma-ray detection.[10] The second and third iterations of the Cryogenic Rare Event Search with Superconducting Thermometers dark matter detector experiment use calcium tungstate as a scintillator as well.[11] It is also utilized in fluorescent lighting systems for its ability to convert ultraviolet light into visible light.[12] In some cathode-ray tubes (CRTs), calcium tungstate (scheelite) is used as a phosphorescent screen material.[13]
In popular culture
Scheelite figures in the manga series Dr. Stone, as a precursor to tungsten, and for its fluorescence.[14]
References
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- ↑ Lindgren, W. (1933) Ore Deposits of the Western States, pp. 518, 535
- ↑ Template:Cite EB1911
- ↑ Amstutz, Gerhard Christian et al. (Ed.). Ore Genesis: The State of the Art. Vol. 2. Springer Science & Business Media, 2012, p. 418.
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Further reading
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- Anderson, B. W., Jobbins, E. A. (Ed.) (1990). Gem testing. Butterworth & Co Ltd, Great Britain. Template:ISBN
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