QUARTZ

Quartz is the most abundant mineral in the Earth's continental crust. Belonging to the family are amethyst, citrine, smoky quartz, rose quartz, as well as chalcedony and other agates. Roman naturalist Pliny the Elder believed quartz to be water ice, permanently frozen after great lengths of time. (The word "crystal" comes from the Greek word for ice.) He supported this idea by saying that quartz is found near glaciers in the Alps, but not on volcanic mountains, and that large quartz crystals were fashioned into spheres to cool the hands. He also knew of the ability of quartz to split light into a spectrum. This idea persisted until at least the 1600's.