Bementite Locality: near Golconda, Humboldt County, Nevada Size: small cabinet, 6.1 x 3.4 x 1.6 cm Bementite A rare locality specimen of bementite, named after noted collector Clarence Bement. I had never seen material from Nevada before. The accompanying label notes that it is here "all the brown material" in which case, this would be quite rich. Ex. John White Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Bementite
Bementite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn₇Si₆O₁₅(OH)₈.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Clay structural group.
Key properties: Mohs hardness 4.5–6; specific gravity 2.98–3.02; Waxy, pearly on perfect cleavage luster; optically biaxial.
IMA symbol Bem, IMA status: approved, named in 1888.
Layered parallel to the walls of secondary veins of calcite in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA); intimately intergrown with other manganese minerals (Olympic Peninsula, Washington, USA).
It is found associated with Calcite, willemite (Franklin, New Jersey, USA); hausmannite, jacobsite, braunite, alleghanyite, barite, grossular, johannsenite, calcite (Olympic Peninsula.
The name refers to Clarence Sweet Bement (1843–1923), American mineral collector of Philadelphia, Pennsylvania, USA.