Smoky quartz is a brownish grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystals. The color of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates color centers around aluminum impurities within the crystalline quartz.

Synthetic smokey quartz can be created through the artificial irradiation of quartz using cobalt-60 or x-rays, however these types of specimens usually have an opaque coating that does not display smokey translucence.