Epistilbite is a extremely user that is uncommon of Zeolite Group of minerals that features over 40 minerals and these gem-type minerals: Analcime, Barrerite, Chabazite, Epistilbite, Gmelinite-Na, Goosecreekite, Mordenite, Natrolite, Pollucite, Scolecite, Stellerite, Stilbite, Thomsonite and Yugawaralite. Epistilbite often forms in the petrified bubbles, called vesicles, of slightly metamorphosed rocks that are volcanic additionally in certain pegmatites.

Although Epistilbite is fairly rare, many localities are understood. Exceptional crystals from around the Berufjord, Iceland. Found near San Piero in Campo, Elba, Italy. At Giebelsbach, near Fiesch, Valais, Switzerland. In Japan, at Kuroiwa, Niigata Prefecture; Yugawara, Kanagawa Prefecture; and elsewhere. Large crystals from Nasik and Khandivali quarry, Bombay, Maharashtra, Asia. In america, big crystals from Kosmos, near Morton, Lewis County, Washington; at Goble, Columbia County, Oregon.

Crystallography: Triclinic – Pinacoidal
Crystal Habit: Crystals prismatic, to 3 cm; in spherulitic or sheaflike aggregates.
Twinning: Always on [100], pseudo-orthorhombic; on [110] to form penetration crosses.


Cleavage: [010] Perfect
Fracture: Irregular/Uneven
Tenacity: Brittle
Hardness (Mohs): 4.0 – 5.0
Density: 2.20 – 2.30 (g/cm3)
Luminescence: None
Radioactivity: Not Radioactive
Other: Piezoelectric


Color: Colorless, White, Yellowish, Pinkish, Brownish White
Transparency: Transparent to Translucent
Luster: Vitreous
Refractive Index: 1.485 – 1.519  Biaxial ( – )
Birefringence: 0.0100
Dispersion: Relatively Strong; r < v
Pleochroism: None