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Tephroite & Zincite with Franklinite

The Mineral tephroite




Tephroite is uncommon member of the Olivine group. It is the manganese counterpart of Forsterite, and forms a series with Forsterite. Tephroite gets it name from the Greek word "tephros", meaning ash-colored, referring to its ash-gray color habit.
Chemical Formula Mn2SiO4
Composition Manganese silicate, sometimes with some magnesium and zinc. Forms a series with Forsterite.
Variable Formula (Mn,Mg,Zn)2SiO4
Color Gray, grayish-green, olive-green, brown, reddish-brown, pink
Streak Light gray
Hardness 6
Crystal System Orthorhombic
Crystal Forms
and Aggregates
As rounded and fractured crystals, usually short and prismatic, but occasionally elongated. Also occurs grainy, massive, and in large cleavage fragments.
Transparency Translucent. Rarely transparent.
Specific Gravity 4.0 - 4.1
Luster Vitreous, greasy, waxy
Cleavage 2,1 ; 3,1- forming a 90º angle
Fracture Conchoidal to uneven
Tenacity Brittle
In Group Silicates; Nesosilicates
Striking Features Cleavage angles, color, and hardness.
Environment In manganese-rich metamorphic deposits.
Rock Type Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 3

Tephroite ON EBAY



NOTEWORTHY LOCALITIES
Worldwide localities for Tephroite include Broken Hill, New South Wales, Australia; the Wessels Mine, Hotazel, Kalahari manganese fields, South Africa; and Langban, Sweden. In the U.S., the most well-known Tephroite is from Franklin, Ogdensburg, and Sparta, all in Sussex Co., New Jersey. Tephroite is also found in the Jail Hill Quarry, Haddam, Middlesex Co., Connecticut.

COMMON MINERAL ASSOCIATIONS
Calcite, Rhodonite, Quartz, Spessartine, Willemite

DISTINGUISHING SIMILAR MINERALS
Willemite - Different cleavage, fluoresces bright green.
Rhodonite - Usually pinker in color.


tephroite PHOTOS
 
ADDITIONAL RESOURCES
 
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