The chemical formula of mineral Tephroite is indicated by the formula Mn2SiO4 or Manganese Silicate. Tephroite is actually a Silicate mineral. It is considered as a very minor ore of manganese. It is also usually used as mineral specimen and is often found exhibiting nice and interesting microscope images when viewed with the aid of petrographic polarizing light microscopes. Tephroite is only one of the unusual mineral found at the famous mines of Sterling Hill and Franklin, New Jersey, USA. Tephroite was named after its typical color which is ash gray. It derived its name from the Greek word tephros or ash colored. In optical mineralogy, Tephroite forms a series with the olivine mineral fayalite.
Mineral Tephroite is most commonly found ash gray color and also olive-green, greenish-blue, pink or brown that can be seen more fascinating when viewed with the aid of polarizing microscopes for mineralogists. Tephroite is also usually found showing vitreous to greasy luster when viewed in reflected light of polarized microscopes used in optical mineralogy. Most crystals of Tephroite are found transparent to translucent in appearance. Tephroite is known to crystallize in the orthorhombic system of crystal formation. The crystal habit of mineral Tephroite as described in the field of optical mineralogy usually include short prismatic to blocky crystals that can be noticed more clearly visible when viewed closely with the aid of polarizing microscopes for mineralogists. Tephroite can be also found massive, granular and compact.
Tephroite is most commonly found showing good cleavage in two directions at 90 degrees which can be seen more clearly visible when specimen sample is evaluated closely with the aid of petrographic polarizing microscopes used in the field of optical mineralogy. Tephroite is also usually found showing uneven to conchoidal fracture when viewed under polarized microscopes for mineralogists. The hardness measure of the mineral when it is evaluated using the Mohs scale method is usually 6. Tephroite is also most commonly found leaving an off white to gray streak when specimen sample is rubbed on a white porcelain streak plate. The specific gravity measure of the mineral is approximately 4.1 grams per cubic centimeters, which is heavy for non-metallic minerals. Tephroite is most commonly found in contact metamorphic and hydrothermal replacement deposits. Tephroite is most commonly found associated with other interesting minerals including quartz, willemite, calcite, Rhodonite, franklinite, spessartine and pyroxmangite. The best field indicators of mineral Tephroite usually include cleavage, crystal habit, hardness, density, environment and color. Tephroite notably occurs at several localities such as Cornwall, England and Langban, Sweden as well as Sterling Hill and Franklin, New Jersey and California, USA.
