Epistilbite: The zeolite mineral epistilbite information and pictures

About

Epistilbite is a rare member of the zeolite group. It has a very similar chemical makeup to Stilbite, and can be difficult to distinguish from Stilbite. Epistilbite is named from the Greek Epi which means "similar" and Stilbite, due to the similarity of this mineral to Stilbite. Epistilbite is not dimorphous with Stilbite, despite its prefix Epi which often implies a dimorph. Interestingly, Epistilbite it dimorphous with a different zeolite, the rare Goosecreekite.

Crystal Forms & Aggregates

Crystals are often prismatic, with distinct chisel-topped terminations. Also globular and in hemispherical, ball-like formations. Other habits in include thin, tabular crystals and groups, columnar, in radiating clusters, and in jagged, haphazard crystals.

Striking Features

Crystal habits and association with other zeolites.

Environment

In air vesicles in volcanic basalt.

Polymorphs

Goosecreekite

Noteworthy Localities

Epistilbite is not a common member of the zeolite group, and good localities are few. Some of the largest crystals come from Berufjördur, Iceland, at Teigarhorn and Fossárfell. Sharp Epistilbite crystal group and aesthetic balls on matrix come from several localities in Maharashtra, India, most notably at Jalgaon, but also at Pune, Nasik, and Ahmadnagar. Small crystals with red inclusions come from Osilo, Sardinia, Italy. In the U.S., colorless micro crystals are found in the Puu o Ehu Quarry, Kailua, Oahu Island, Hawaii.