Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : Ca₁₂Al₂Si₁₈O₅₁ 18H₂O
    Rarity : Uncommon

Tacharanite is a hydrated silicate close to zeolites with which it is also frequently associated in fractures and cavities of basic igneous rocks (basalts, more rarely olivine dolerite and metagabbros) and in their enclaves, sometimes in rocks very deficient in silica (olivine nephelinite). It is a low-temperature hydrothermal mineral (it crystallizes below 250°C) which would alter into tobermorite, gyrolite and xonotlite. Its name comes from the Gaelic tacharan (fairy child, substituted for a child they stole), because the mineral, when left in the air, dehydrates into other compounds. Tacharanite forms tiny micron-sized fibers, agglomerated in sheaves or spherulites, and cryptocrystalline porcelana masses, always white to milky white in color.

Main photo : Tacharanite from Puech de Vermus, Espalion, Aveyron, France © Elmar Lackner

No twinning known for this mineral species.

No fakes listed for this mineral species.