San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
[Gold on quartz. Collection of the San Diego Natural History Museum.]

Gold

Thought to be from an Anglo-Saxon word, geld, for yellow.

Description and Occurrence

Gold is one of the rarest and most valuable minerals on Earth. It occurs as a native metal, which means it can be found in an uncombined metallic form. It usually formss in small grains or flakes. Nuggets can be found in alluvial or glacial deposits. It rarely forms as crystals. Gold's yellow color and brightness vary with the amount and type of impurities in it. It's ideal for jewelry and ornamentation because it's both malleable and durable.

A shiny yellowish mineral called Pyrite is often mistaken for gold. Don't be fooled by this "fool's gold"!

One third of the world's gold is mined in South Africa. Other sources for gold are Australia, Russia, and the United States.

In 1869, gold was discovered at Coleman Creek in the mountains on the eastern edge of San Diego County. A gold-mining boom led to the settlement and growth of the mining town of Julian, where artifacts of the gold rush era can be seen at the Julian Pioneer Museum. The Stonewall Jackson Mine, the most productive of the historic gold mines in the county, is included within Cuyamaca Rancho State Park.

Field Notes: Gold has a high specific gravity (it's heavy), is soft and malleable, and leaves a yellow streak.


Physical Properties

Color Streak Transparency Luster Hardness Cleavage Fracture Specific gravity Crystal form
gold-yellow, brass-yellow, pale yellow gold-yellow opaque metallic 2.5 to 3 none hackly 15.5 to 19.3 isometric

Photo: Photo: Gold embedded in quartz.
Collection of the San Diego Natural History Museum
Photo credit: Tim Murray

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