Native metal brass, bronze, pewter, German silver, osmiridium, electrum, white gold, and silver-mercury and gold-mercury amalgam. Only gold, silver, copper and the platinum metals occur in nature in large amounts. Over geological time scales, very few metals can resist natural weathering processes like oxidation, which is why generally only the less reactive metals such as gold and platinum are found as native metals. The others usually occur as isolated pockets where a natural chemical process reduces a common compound or ore of the metal, leaving the pure metal behind as small flakes or inclusions. Non-metallic elements occurring in the native state include
Argentine Pass iron pyrite, cupriferous pyrite (chalcopyrite), and some tetrahedrite. This was the first major discovery of silver ore in Colorado. They named the deposit the Belmont Lode (from the French for "beautiful mountain"), and the surrounding area came to be known as the Argentine mining district (from "argentum", Latin for silver). The discovery led to the growth of Georgetown as an early center of the silver mining industry in Colorado, although development was slowed by a general ignorance of how to properly treat the ore, by the high cost of transportation from the mines, and by the climate at that altitude.