Zeolite: A class of silicates containing H=O in cavities within the crystal structure. Formed by alteration at low temperature and pressure of other silicates, often volcanic glass.

Zoned crystal: A single crystal of one mineral that has a different chemical composition in its inner and outer parts. Formed from minerals belonging to a solid-solution series, and caused by the changing concentration of elements in a cooling magma that results from crystals settling out.