thortveitite

{{Short description|Sorosilicate mineral}}

{{Infobox mineral

| name = Thortveitite

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| image = Thortveitite-ea14a.jpg

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| caption = Thortveitite

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| formula = (Sc,Y)₂Si₂O₇

| IMAsymbol = Tvt{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

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| strunz = 9.BC.05

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| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = C2/m

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| mohs = 5–6

| luster = vitreous

| streak = gray

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| gravity = 3.3–3.8

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Thortveitite is a rare mineral consisting of scandium yttrium silicate (Sc,Y)₂Si₂O₇. It is the most widespread scandium mineral,{{mindat|url=https://www.mindat.org/element/Scandium|title=Scandium|access-date=2025-05-29}} but natural thortveitite is not widely exploited as a source of scandium metal. Most scandium is derived from mine tailings, which can include thortveitite.{{cite web |url=https://www.stanfordmaterials.com/blog/an-overview-of-scandium.html |title=Properties of Scandium |last=Lowen |first=Eric |website=Stanford Advanced Materials |access-date=Sep 24, 2024}} Thortveitite mining in the United States ceased in 1969.{{cite web|url=https://pubs.usgs.gov/periodicals/mcs2025/mcs2025-scandium.pdf|publisher=U.S. Geological Survey|website=National Minerals Information Center|author=Shelby Johnston|title=Mineral Commodity Summaries 2025: Scandium|access-date=2025-05-29}}

Occurrence is in granitic pegmatites. It was named after Olaus Thortveit, a Norwegian engineer. It is grayish-green, black or gray in color.{{Cite web|title=Thortveitite Mineral Data|url=http://webmineral.com/data/Thortveitite.shtml#.YI_Dr7UzZEY|access-date=2021-05-03|website=webmineral.com}}{{Cite web|title=Thortveitite|url=https://www.mindat.org/min-3950.html|access-date=2021-05-03|website=www.mindat.org}}{{Cite journal|last1=Bianchi|first1=Riccardo|last2=Pilati|first2=Tullio|last3=Diella|first3=Valeria|last4=Gramaccioli|first4=Carlo Maria|last5=Mannucci|first5=Gregorio|date=1988-06-01|title=A re-examination of thortveitite|url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/73/5-6/601/105009/A-re-examination-of-thortveitite|journal=American Mineralogist|language=en|volume=73|issue=5–6|pages=601–607|issn=0003-004X}}{{Cite book|url=https://www.worldcat.org/oclc/610708490|title=Mineralien aus aller Welt|date=1990|others=Walter Schumann|isbn=978-3-405-14003-8|location=München|oclc=610708490}}

A transparent gem quality example was found in 2004, and reported in The Journal of Gemmology.{{Cite journal|last=Chapman, R., Mercer, I.F., Rankin, A.H., Spratt, J.|date=2008|title=Thortveitite – a new gemstone|url=https://gem-a.com/images/Documents/JoG/JoG2009_31_5-8.pdf#page=3|journal=Journal of Gemmology|volume=31|issue=1 |pages=1–6|doi=10.15506/JoG.2008.31.1.1|bibcode=2008JGem...31....1C }}