Epistilbite Locality: Jalgaon District, Maharashtra, India (Locality at mindat.org) Size: 10.5 x 5.8 x 4.6 cm. This is another fine example of open space in a v — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Epistilbite
Epistilbite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₃[Si₁₈Al₆O₄₈]·16H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Mordenite structural group.
Key properties: Mohs hardness 4; specific gravity 2.22–2.28; typically white or pink or colorless; white streak; Vitreous luster; optically biaxial.
IMA symbol Estb, IMA status: approved, named in 1826.
Found in cavities in basalts and gneisses.
It is found associated with Zeolites, quartz.
The name comes from the Greek, epi for near, and the quite similar mineral stilbite.
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