Zeolites are aluminosilicate (containing aluminum, Al, and Silicon, Si) minerals that usually contain a large amount of water.   
 

This group of minerals was named in 1756 by Axel Fredrik Cronstedt, a Swedisth mineralogist who heated a mineral, which was probably stilbite, and it produced lots of steam.

For example stilbite has the formula NaCa4(Al9Si27O72).28H2O (that's 28 parts water for every molecule). There are over 40 naturally occuring minerals in the zeolite group, and more than 200 are made by industry..

 
 

Many of the specimens in this exhibit are from India, where large quantities of zeolites have been collected from basalt.

Zeolites form where volcanic rocks and ash interact with alkaline groundwater, or over a long time, even millions of years, in shallow marine basins.

In addition to forming naturally, zeolites are made by industry. Zeolite crystals have a very open structure, and they can be used for water purification and other types of filtering.