Cryolite - AgCl

Habit: Cubic crystals, in parallel or subparallel groups; rarely as stalactites or aggregates; fibrous. Typically massive, forming crusts and films. Colorless, pale yellow or gray, turns violet-brown to purple on exposure to light. Transparent to translucent, resinous to Adamantine Luster.

Environment: Found in the oxidized zone above silver deposits; commonly preserved in arid climates

Etymology: For chlorine, and the Greek for silver, argyros, in its composition