Chrysocolla

Chrysocolla forms in the oxidized zone of copper deposits together with other secondary copper minerals, typically as glassy botryoidal or rounded masses, bubbly crusts and vein fillings; any fibrous "crystals" are pseudomorphs. Sources include the western United States (especially Arizona, New Mexico, Nevada, Utah and Idaho), Katanga in the Democratic Republic of the Congo, Chile, Israel, Mexico and Russia.

Chrysocolla's hardness varies widely: a coin can scratch soft material, while silica-rich material reaches 7. Related materials include chrysocolla chalcedony (marketed as "gem silica"), a chalcedony coloured by fine chrysocolla inclusions; Eilat stone, a mix of chrysocolla, malachite, turquoise and other minerals from Eilat, Israel; "stellarite", a trade name for light blue chrysocolla with quartz; and "parrot-wing", chrysocolla mixed with jasper. Chrysocolla itself is not commonly treated, but dyed chalcedony is sold as an imitation of chrysocolla and of chrysocolla-in-chalcedony; GIA reported dyed pieces with copper concentrated near the surface and no Raman peak of chrysocolla. Copper-bearing allophane can look similar.

Because hardness ranges from about 2 to 7, treat a stone of uncertain composition gently. Avoid steam and ultrasonic cleaning; use a soft brush, mild detergent and warm water. Store chrysocolla separately from other stones to avoid scratches.

The name was first used by Theophrastus in 315 BCE, from the Greek "chrysos" (gold) and "kolla" (glue), after a material the ancient Greeks used to solder gold; the name was revived for the mineral in 1808 by André-Jean-François-Marie Brochant de Villiers. Eilat stone, a chrysocolla-bearing mixture, is regarded as the national stone of Israel and is also called the "King Solomon Stone".