A massive specimen, with a sawn surface. Collection and photo Erik Vercammen. From: Watsons Beach, Clutha District, Otago Region, New Zealand. — Photo: Erik Vercammen · CC BY 3.0
Coombsite
Coombsite is an IMA-recognized mineral species in the silicate class, with the chemical formula KMn²⁺₁₃(Si,Al)₁₈O₄₂(OH)₁₄.
It crystallizes in the tetragonal crystal system.
Key properties: specific gravity 3; optically uniaxial.
IMA symbol Cmb, IMA status: approved, named in 1989.
Found in a manganese-rich rock in metagraywacke-argillite in the pumpellyite-prehnite facies.
It is found associated with Rhodonite, quartz, rhodochrosite, kutnohorite, manganoan calcite, spessartine, apatite, parsettensite, caryopilite.
The name refers to Professor Douglas Saxon Coombs (1924{), mineralogist and petrologist, University of Otago, Dunedin, New Zealand.