Black crystals of the very rare mineral taneyamalite from the type (Taneyama Mine, Kumamoto Prefecture, Kyushu Region, Japan) and one of the only five known localities worldwide. — Photo: David Hospital · CC BY-SA 4.0
Taneyamalite
Taneyamalite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Na,Ca)Mn²⁺₁₂(Si,Al)₁₂(O,OH)₄₄.
It crystallizes in the triclinic crystal system.
Key properties: Mohs hardness 5–6; specific gravity 3.3; Light yellow, brown streak; Vitreous luster; optically biaxial.
IMA symbol Tny, IMA status: approved, named in 1977.
Found in cracks in ferruginous chert, mafic rocks, and limestone subjected to blueschist facies metamorphism (Taneyama mine, Japan).
It is found associated with Quartz, hematite, chamosite (Taneyama mine, Japan); caryopilite, bannisterite, braunite, rhodochrosite, calcite, albite, cinnabar, pyrite (Iwaizawa mine, Japan).
The name refers to the Taneyama mine, Japan, where the mineral was first noted.