|
Chalcedony
A cryptocrystalline,
translucent variant of quartz composed of silica, having usually a whitish co
lour, and a waxy luster. Chalcedony was named after Chalkedon, near Istanbul.
It has traditionally been used for decorative objects and amulets. It has a relative
hardness of 7. When chalcedony is variegated with spots or figures, or arranged
in differently colored layers, it is called agate; and if by reason of the thickness,
co lour, and arrangement of the layers, it is suitable for being carved into cameos.
Chrysophrase is green chalcedony; carnelian, a red or deep orange; black or dark
red, it is called onyx, and sard, a brownish red variety.
Chrysocolla
Harder than turquoise, softer than chalcedony, non-cleaving, vitreous, streaky white to pale blue or green, often associated with limonite, malachite and azurite. It is a minor ore of copper.
Chrysophrase
Apple-green to bluish chalcedony, comes from Australia, Arizona, California and Oregon.
|
|
|
|
