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Tephroite
Chemical Formula	Mn2SiO4
Species	Silicates
Crystal System	Orthorhombic
Mohs Scale	6
Specific Gravity	3.87-4.12
Color	Olive-green, bluish green, gray, °esh-red, reddish brown; pale green in thin section, may be colorless
Streak	Pale gray
Luster	Vitreous, Greasy
Refractive Index	n = 1.759 n = 1.797 n = 1.860
Diaphaneity	Translucent
Cleavage	Distinct/GoodDistinct on Imperfect on
Fracture	Irregular/Uneven, Conchoidal
Crystal Habit：Crystals typically short, prismatic, to 4 cm, or anhedral, equidimensional. Commonly in disseminated grains, compact, or massive.
Geological Setting：In Fe-Mn ore deposits, skarns, and metamorphosed manganese rich sediments.

It was first described for an occurrence at the Sterling Hill Mine and Franklin, New Jersey, USA. 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. 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. It can also be found olive-green, greenish-blue, pink, or brown.