Zeolite

Zeolites typically form in low-temperature hydrothermal systems, especially in volcanic and volcanically derived rocks, and define the "zeolite facies" of metamorphism. A major source of collector specimens is the Deccan Traps of western India, where zeolites fill gas cavities (amygdales) and veins in basalt lava flows and are recovered from construction-stone quarries around Mumbai, Pune, Nashik and Jalgaon.

Because "zeolite" covers many species, a stone sold under that name alone has not been identified to species. Cavity minerals from the Indian basalts have often simply been called "zeolites", although the same cavities also yield non-zeolite minerals such as apophyllite, okenite and calcite. Telling the species apart requires laboratory methods such as X-ray diffraction and electron microscopy, as used in studies of Deccan zeolites.

The name was coined in 1756 by the Swedish mineralogist Axel Fredrik Cronstedt, who described a new hydrated mineral that frothed and puffed up when heated in a blowpipe flame; he coined the name to recall this frothing property. His Swedish specimen came from the Svappavaara copper mine area near Kiruna; the original material has been reported to be stilbite.

The Japanese retailer Pascle says zeolite has long been regarded as a healing stone with strong purifying power, a belief it links to the mineral's real adsorption properties, and says wearing it is believed to ease stress and fatigue. These are retailer beliefs, not tested properties.