Only gold, silver, copper and the
platinum metals occur in nature in larger 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 carbon and sulfur. Silicon, a semi-metal, has been found
in the native state on rare occasions as small inclusions in gold.
Native metals were prehistoric man's
only access to metal, since the process of extracting metals from their ores,
smelting, is thought to have been discovered around 6500 BC. However, they
could be found only in relatively small amounts, so they could not be used
extensively. So while copper and iron were known well before the copper age and
Iron Age, they would not have a large impact on humankind until the technology
to smelt them from their ores, and thus mass-produce them appeared. The gold
group consists of gold, copper, lead, aluminium, mercury, and silver. The
platinum group consists of platinum, iridium, osmium, palladium, rhodium, and
ruthenium. Amongst the alloys found in native state have been brass, bronze,
pewter, German silver, osmiridium, electrum, white gold, and silver-mercury and
gold-mercury amalgam.