Apophyllite

The name apophyllite refers to a specific group of phyllosilicates, a class of minerals. The name apophyllite derived from the Greek apophyllízo, meaning ‘it flakes off’, a reference to this class’s tendency to flake apart when heated, due to water loss. Exfoliation of apophyllite is also possible by treating it with acids or simply by rubbing it.

These minerals typically found as secondary minerals in vesicles in basalt or other volcanic rocks.