Ganterite
Ganterite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ba₀.₅(Na,K)₀.₅Al₂(Si₂.₅Al₁.₅)O₁₀(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 4–4.5; specific gravity 3.11; White streak; Vitreous luster; optically biaxial.
IMA symbol Gtr, IMA status: approved, named in 2000.
A rock forming mineral in bands and lenses of white-mica schists and in zoisite– celsian gneiss.
It is found associated with Muscovite, zoisite, quartz, plagioclase, apatite, zircon, amphibole (schist); zoisite, celsian, quartz, margarite ± armenite (gneiss); dumortierite, barite.
The name refers to Gantertal, a valley in the Simplon region that produced the first specimens.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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