Bementite

minerals

inesite

willemite

Formula: Mn7Si6O15(OH)8
Unclassified silicate, manganese-bearing mineral
Specific gravity: 2.9 to 3.1
Hardness: 6
Streak: White
Colour: Brown, dark brown, golden brown, greyish-yellow
Common impurities: Al,Fe,Zn,Mg,Ca
Environments

Metamorphic environments

Bementite is found in low-grade metamorphic manganese silicate deposits (Mindat).

Localities

At the Hale Creek Mine, Mad River Rock, Coastal Range, Trinity county, California, USA, bementite is associated with hausmannite, rhodochrosite and inesite (HOM).

At the type locality, the Trotter Mine, Franklin Mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA, bementite was found layered parallel to the walls of secondary veins of calcite in a zinc-iron oxide ore deposit hosted in marble, associated with calcite and willemite (HOM, Mindat).

On the Olympic Peninsula at a number of small deposits in Clallan, Jefferson, and Mason counties, Washington, USA, bementite is associated with hausmannite, jacobsite, braunite, alleghanyite, baryte, grossular, johannsenite and calcite (HOM).

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