{{distinguish|tephrite}} {{infobox mineral | name = Tephroite | category = Silicate mineral | boxwidth = | boxbgcolor = | image = Tephroite Manganese silicate Kaao Mine Tochigi-ken Honshu Japan 1816.jpg | imagesize = | alt = | caption = Tephroite from Japan | formula = Mn<sub>2</sub>SiO<sub>4</sub> | IMAsymbol = Tep<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|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|url-access=subscription}}</ref> | molweight = | strunz = | dana = | system = Orthorhombic | class = Dipyramidal (mmm) <br/>H-M symbol: (2/m 2/m 2/m) | symmetry = ''Pnma'' (no. 62) | unit cell = a = 4.88(2)&nbsp;Å, b = 10.61(2)&nbsp;Å <br/>c = 6.24(2)&nbsp;Å; Z&nbsp;=&nbsp;4 | color = Olive-green, bluish green, gray, °esh-red, reddish brown; pale green in thin section, may be colorless | colour = | habit = Crystals typically short, prismatic, to 4 cm, or anhedral, equidimensional. Commonly in disseminated grains, compact, or massive. | twinning = Uncommon on {011} | cleavage = {010}, distinct; {001}, imperfect | fracture = Uneven to conchoidal | tenacity = Brittle | mohs = 6 | luster = Vitreous to greasy | streak = Pale gray | diaphaneity = Transparent to translucent | gravity = 3.87 – 4.12 | density = | polish = | opticalprop = Biaxial (−) | refractive = n<sub>α</sub> = 1.759 n<sub>β</sub> = 1.797 n<sub>γ</sub> = 1.860 | birefringence = δ = 0.101 | pleochroism = Weak; X = brownish red; Y = reddish; Z = greenish blue. | 2V = Measured: 60° to 70°, Calculated: 78° | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = <ref name=Handbook>http://rruff.geo.arizona.edu/doclib/hom/tephroite.pdf Handbook of Mineralogy</ref><ref name=Mindat>http://www.mindat.org/min-3913.html Mindat.org</ref><ref name=Webmin>http://webmineral.com/data/Tephroite.shtml Webmineral data</ref> }} '''Tephroite''' is the manganese endmember of the olivine group of nesosilicate minerals with the formula Mn<sub>2</sub>SiO<sub>4</sub>. A solid solution series exists between tephroite and its analogues, the group endmembers fayalite and forsterite. Divalent iron or magnesium may readily replace manganese in the olivine crystal structure.

It was first described for an occurrence at the Sterling Hill Mine and Franklin, New Jersey, United States.<ref name=Mindat/> It occurs in iron-manganese ore deposits and their related skarns. It also occurs in metamorphosed manganese-rich sediments. It occurs in association with: zincite, willemite, franklinite, rhodonite, jacobsite, diopside, gageite, bustamite, manganocalcite, glaucochroite, calcite, banalsite and alleghanyite.<ref name=Handbook/> It can also be found in England and Sweden.

Tephroite has a hardness of 6 and a specific gravity of approximately 4.1, which is heavy for non-metallic minerals. Its name comes from the Greek ''tephros'', "ash gray", for its color.<ref name=Webmin/> It can also be found olive-green, greenish-blue, pink, or brown. Other names for tephroite include mangan olivine and mangan peridot.

==References== {{Reflist}} *[https://web.archive.org/web/20061017063718/http://mineral.galleries.com/minerals/silicate/tephroit/tephroit.htm Mineral galleries]

{{Manganese minerals}}

Category:Manganese(II) minerals Category:Nesosilicates Category:Orthorhombic minerals Category:Minerals in space group 62

{{silicate-mineral-stub}}