sodalite var. hackmanite, winchite : Koksha Valley (Kokscha Valley ; Kokcha Valley), Khash & Kuran Wa Munjan Districts, Badakhshan Province (Badakshan Province ; Badahsan Province), Afghanistan — Photo: Parent Géry · CC BY-SA 3.0
Winchite
Winchite is an IMA-recognized mineral species in the silicate class, with the chemical formula (NaCa)(Mg₄Al)Si₈O₂₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 5–6; specific gravity 2.97–3.17; [Vitreous.] luster; optically biaxial.
IMA symbol Wnc, IMA status: approved, named in 1906.
Found in schists with low-grade metamorphosed manganese deposits; in metabasalts of the jadeite-glaucophane and amphibolite-eclogite facies; in manganiferous cherts that have undergone blueschist facies metamorphism.
It is found associated with Calcite, microcline, diopside, plagioclase, apatite, tremolite (Ka jlidongri mine, India); omphacite, garnet, rutile, quartz, actinolite, epidote, albite.
The name refers to H.J. Winch, who first found the mineral.