Copper occurs naturally in its native state in a variety of forms these include large or "massive" pieces, thin wires, and extensive branch like shapes. It can sometimes also be found in mines and quarries as precipitates where iron-bearing structures such a pipes are in contact with the ground. It used to be one of the main sources of copper; however, thousands of years of human extraction have more or less developed it as an industrial source. Fine specimens are highly sought after by collectors though, especially if they display good crystal structures. Native copper usually has a dark tarnish, and has to be chemically cleaned to obtain the bright copper colored finish.
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