Microcrystals of the rare manganese mineral neltnerite from Manganese Creek in Michigan: Manganese Creek, Keweenaw Co., Michigan, United States of America. — Photo: David Hospital · CC BY-SA 4.0
Neltnerite
Neltnerite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaMn³⁺₆O₈(SiO₄).
It crystallizes in the tetragonal crystal system (space group I4_1/acd). It is a member of the Braunite structural group.
Key properties: Mohs hardness 6; specific gravity 4.63; Submetallic. Anisotropism: Weak. R1 {R 2: (470) 21.3–22.3, (546) 19.2–20.2, (589) 18.5–19.5, (650) 17.65–18.65 luster.
IMA symbol Nel, IMA status: approved, named in 1979.
Found in a vein with minerals containing manganese and calcium (Tachgagalt, Morocco).
It is found associated with Braunite, marokite, crednerite (Tachgagalt, Morocco).
The name refers to Louis Neltner, pioneer student of mineral deposits of the High Atlas Mountains, Morocco.