San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
[Dendritic copper. Collection of the San Diego Natural History Museum.]


From the Greek, Kyprios, for the island of Cyprus, where copper was found and mined.

Description and Occurrence

Copper generally forms in compact masses (lumps) or dendritic masses (irregular, tree-like shapes). It rarely forms as crystals. It has a characteristic copper-red color on freshly broken or scratched surfaces. More often it's covered with a light film of tarnish, which can be black, blue, or green. Copper is a native metal, which means it can be found in an uncombined metallic form.

Copper is easily extracted from rocks, and people have used it for thousands of years to make tools and jewelry. It conducts heat and electricity. It's very malleable and can be hammered thinly without breaking. It's used in electrical apparatus and wire, electronic equipment, roofing materials, tools, coins, and plumbing. Copper alloys include brass and bronze.

A copper deposit discovered in 1860 near the gulf coast of Baja California Sur was mined from the 1880s to 1954 by a French company under a concession from the Mexican government. The company built the town of Santa Rosalía, its port, and other public buildings, and imported a prefabricated galvanized iron church designed by Alexandre Gustave Eiffel. The ore-processing plant and its conveyor belts, and the wooden frame architecture of Santa Rosalía, remain as a sign of the town's coppery history.

Field Notes: Copper is very soft. Scratching the surface shows its distinctive copper-red color.

Physical Properties

Color Streak Transparency Luster Hardness Cleavage Fracture Specific gravity Crystal form
copper-red, tarnishes to black, blue, green copper-red opaque metallic 2.5 to 3 none hackly 8.9 isometric

Photo: Dendritic copper. Collection of the San Diego Natural History Museum
Photo credit: Linda West

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