Strontiomelane
The strontium member of the hollandite family — a tunnel-structured manganese oxide.
Intro adapted from Wikipedia (CC BY-SA).
Strontiomelane is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Sr(Mn⁴⁺₆Mn³⁺₂)O₁₆.
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Coronadite structural group.
Key properties: specific gravity 4.66; Sepia streak; Submetallic luster.
IMA symbol Sml, IMA status: approved, named in 1995.
Found as a primary mineral in meta-ophiolite rocks (amphibolite-eclogite facies), the Mn deposit originally of seafloor hydrothermal origin.
It is found associated with Braunite, hollandite, cryptomelane, fluorapatite, titanite, jadeite, strontiopiemontite.
The strontium analog of cryptomelane. The name alludes to the composition, strontio, and the Greek melas, -anos, for black.