Copper, Onganja Mine, Emke Farm, Namibia
description: 1 7/8" ac This crystallized copper displays a combination of octahedral crystals and spinal twins. Although this piece is copper red, I do not believe it has been dipped in acid. Copper from many localities (including Ajo, Arizona) is also copper red instead of chocolate brown, black or greenish. The determinant of patina color is the composition of the alloy of the specimen. Native copper is often alloyed with other metals which can alter the surface of the specimen reacts with other elements in its environment. Onganja is a copper mine that no longer produces and few copper specimens were found there when it was producing. This is only one of fewer than 10 copper specimens I have seen from this locality over the years.
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