These sheaf-like bundles of stilbite crystals were deposited by hot, water-rich solutions in cavities and fractures in volcanic rock. The color variations are caused by the many different orientations of the crystals in the thin section. Stilbite is a member of the mineral family called zeolites. Submicroscopic tunnels in their crystal structure, as well as their chemically sticky surfaces, make zeolites excellent natural filters. This leads to many industrial applications such as ion exchangers in water softeners, and as molecular sieves.

Crossed polarizers