Throughout human history, gold has been the most prized of metals. Golds brightness and color are highly attractive, gold is extremely malleable, and it’s usually found in nature in a relatively pure form. All of these qualities and properties have made gold exceptionally valuable. Gold is also remarkably inert (not chemically active) and gold neither bonds nor reacts with most chemicals, so it naturally resists tarnishing.
Since the civilizations of ancient Egypt and Mesopotamia, people have been using gold. In ancient times, gold was almost exclusively recovered from river and stream beds and placer deposits (open-pit mining), where particles of gold weathered from its original rock. Gold is rarely found in well formed crystals, but more commonly gold occurs as dendritic growths and as grains and scaly masses. Virtually all igneous rocks contain gold in low concentrations, where it occurs mostly as invisible, disseminated grains. Within the Earth’s crust, Gold’s abundance is estimated at roughly 0.005 parts per million.
One unusually rich concentration of gold minerals was discovered at the famous Colorado gold-rush town of Cripple Creek in 1891 by a cowboy and part-time prospector, which later transformed the sleepy ranching community into one of the world’s richest gold camps. Three mines still operate today: Mollie Kathleen, the Cripple Creek Mine, and the Victor Gold Mine.
Large masses of rock rich enough to mine only for the gold are rare. Usually, Gold is mined typically in two ways: hydrothermal veins, where gold is associated with quartz and pyrite (commonly referred to as Fool’s Gold); and placer (open-pit mining) deposits. Smaller quantities of gold often occur in copper and lead deposits, where gold is recovered as a byproduct in the refining of the primary extraction metal.
The pricipal ancient sources of gold were southern Sudan and egypte. Major sources in Europe during the Middle Ages were the mines of Saxony and Austria. The largets single gold-ore body known to the modern world is located in South Africa’s Witwatersrand. Thalf of the Earth’s known gold reserves are in South Africa, with other large deposits in Russia, Brazil, Canada, Australian, and the U.S.