Tephroite is the

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy u ...

endmember of the

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

group of

nesosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually cons ...

minerals with the formula Mn₂ Si O₄. A solid solution series exists between tephroite and its analogues, the group endmembers

fayalite Fayalite (, commonly abbreviated to Fa) is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system ( space group ''Pbnm'') with cell para ...

and

forsterite Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite. Forsterite crystallizes in the ort ...

. 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. It occurs in iron-manganese

ore deposit Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April ...

s and their related skarns. It also occurs in metamorphosed manganese-rich sediments. It occurs in association with: zincite, willemite,

franklinite Franklinite is an oxide mineral belonging to the normal spinel subgroup's iron (Fe) series, with the formula ZnFe3+2O4. As with another spinel member magnetite, both ferrous (2+) and ferric (3+) iron may be present in Franklinite samples. Diva ...

, rhodonite, jacobsite,

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dul ...

, gageite, bustamite,

manganocalcite Manganoan calcite or manganocalcite is a variety of calcite rich in manganese, which gives the mineral a pink color.Mang ...

, glaucochroite,

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...

banalsite Banalsite is a rare barium, sodium aluminium silicate mineral with formula: BaNa2Al4Si4O16. Banalsite is a tectosilicate of the feldspar group. Banalsite and its strontium analogue, stronalsite (SrNa2Al4Si4O16), constitute a complete solid soluti ...

and alleghanyite. It can also be found in

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

and Sweden. Tephroite has a hardness of 6 and a

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...

of approximately 4.1, which is heavy for non-metallic minerals. Its name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''tephros'', "ash gray", for its color. It can also be found olive-green, greenish-blue, pink, or brown. Other names for tephroite include mangan olivine and mangan peridot.

References

Mineral galleries
Manganese(II) minerals Nesosilicates Orthorhombic minerals Minerals in space group 62 {{silicate-mineral-stub