Copper

Copper is found in native form in many places. This wiry aggregate, shown about twice life size, formed as metal-bearing fluids worked their way into channels and pore spaces in a preexisting matrix, probably near a volcanic zone. There are many different scenarios that mobilize and redeposit copper in the upper crust.

This copper nugget (shown about four times life size) comes from a streambed in some place like Minnesota or Michigan's Upper Peninsula, which was a copper district for many years. There copper metal appears in extremely old rocks of the Canadian Shield. This nugget is soft enough to bend in your hands. Copper has a distinctive copper-colored streak. Copper was not as useful for the ancients as the alloy bronze, which includes tin metal and is much more durable. Today copper is one of the most important metals, used in electrical equipment, alloys, coatings, and computer chips.

Because native copper corrodes fairly quickly at surface conditions, nuggets like this don't last long (unlike gold).

Native copper is no longer an important source of the metal. Today copper comes from huge low-grade deposits, mined by large companies that have a very small profit margin but make up for it in volume. Impurities in copper, including silver and gold, are important byproducts.

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