White Chalcedony

Chalcedony forms at relatively low temperatures from silica-rich waters, commonly as botryoidal crusts lining or filling cavities and fissures in volcanic rocks, and also in sedimentary rocks. White chalcedony "roses" weather out of volcanic rock in places such as the Mopah Range of the Turtle Mountains, California, and occur in Irai, Rio Grande do Sul, Brazil.

White chalcedony shows the waxy luster, translucency, lack of cleavage and quartz hardness of all chalcedony, with a refractive index of about 1.54 to 1.55 and specific gravity near 2.6. "Chinese opal" is a misnomer sometimes applied to white chalcedony; it is not opal. Chalcedony is porous and light-colored material is easily dyed, so pale chalcedony is also the usual starting material for dyed colors.

Chalcedony is a tough gem suitable for all kinds of jewelry and needs no special care. Clean it with mild detergent, warm water and a soft brush.

These records concern chalcedony in general rather than this color specifically. The name is generally traced to the ancient port of Chalcedon, now Kadıköy in Istanbul, Turkey; Agricola mentioned a stone named for the town in 1546. Chalcedony was used for cylinder seals in Mesopotamia as early as the 7th century BC and later for jewelry, buttons, cameos and intaglios.

Chalcedony in general was traditionally believed to drive away melancholy and evil spirits; Merrill (1922) recorded the belief that, worn as an amulet, it guarded against danger during tempests. It is also listed in the Bible (Revelation 21:19) as the third foundation stone of the Heavenly City.