Rocks, Gems, and Minerals by Garret Romaine

Author:Garret Romaine
Language: eng
Format: epub
Publisher: Falcon Guides
Published: 2020-03-21T00:00:00+00:00

Chrysocolla

Striking blue chrysocolla resembles turquoise.

PHOTO COURTESY OF THE RICE NORTHWEST MUSEUM OF ROCKS AND MINERALS

(Cu,Al)2H2Si2O5(OH)4·nH2O

Family: Silicate

Mohs: 2½–3½

Specific gravity: 1.9–2.4

Key test(s): Soft

Likely locale(s): Copper-producing regions

Chrysocolla is a pleasing blue or green material, usually banded, and softer than turquoise. It produces a streak that is slightly blue-green in color, which is helpful. Its luster is vitreous to dull, and it forms in botryoidal masses or coatings rather than as crystals. Chrysocolla oxidizes from copper deposits. Its softness precludes it from being an important lapidary material, but it will take a polish.

There are numerous chrysocolla deposits throughout the copper-mining regions of the Rockies, such as the Bay Horse and Seven Devils districts of Idaho. In Wyoming, search the copper-mining areas in Albany and Carbon Counties. Montana is a major copper-producing state, thus, the area around Butte is noteworthy among hundreds of locales. Colorado also boasts numerous chrysocolla deposits.

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