What is Epistilbite?
Epistilbite is a hydrated calcium aluminosilicate zeolite known for delicate prismatic crystals and sheaf-like aggregates in volcanic cavities.
Mineralogy and structure
Reference formula: CaAl2Si6O16·5H2O. Epistilbite is a hydrated framework silicate with monoclinic or locally lower-symmetry ordering. The water content and partial aluminium-silicon ordering are important parts of its crystal chemistry.
Colour and appearance
Typical colours include colourless, white, pink, salmon. The usual prismatic, spherulitic, radiating habit and vitreous, pearly lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Epistilbite forms in or is associated with basaltic cavities, altered volcanic rocks and low-temperature hydrothermal zeolite assemblages. Important documented localities include Iceland, Switzerland, India, Japan, Italy and the United States.
Collecting and care
Protect from impact, abrasion and strong heating; zeolite crystals can lose water or develop surface damage in unsuitable storage.
Epistilbite in popular symbolism
Modern crystal guides sometimes associate Epistilbite with symbolic themes based on colour or collecting tradition. These associations are cultural interpretations, not mineralogical or medical properties.
