is the most abundant
mineral in the
Belonging to the family are amethyst, citrine, smoky quartz, rose
quartz, as well as chalcedony and other agates.
Pliny the Elder
believed quartz to be water
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
idea persisted until at least the 1600's.