Ancient gold was produced by nature and discovered by the ancients.
According to the Ming Dynasty Song Yingxing book "Tian Gong Kaifu" book records to the effect that: China's gold-producing areas, there are about 100 places, it is difficult to enumerate. Mountain stone in the production, the name of the large horseshoe gold, in the name of the olive gold, with crotch gold, the name of the small melon gold.
Water and sand in the production of the big name of the dog's head gold, the small name of the bran wheat gold or chaff gold. The flat ground digging wells to get, called the face of sand gold, the big name of the bean grain gold. But all of them have to be smelted after panning before they can become a whole piece of gold.
Because the chemical properties of gold is very stable, so the gold in nature is mainly monomers. In ancient times, when productivity levels were relatively low, people used the method of digging in the so-called "gold mountain", and then using a special sieve in the water to sift off the soil to get the gold. Finally, the small gold particles were placed in molds, heated at high temperatures to melt them, and then cooled and turned into gold nuggets for easy preservation.
Extended Information
The types of gold deposits are complex and diverse. There are mainly conglomerate type, greenstone belt type, quartz vein type, ductile shear zone type, Carlin type, porphyry type, shallow into the low temperature hydrothermal type, volcanic rock type, Cenozoic alluvial ore and so on.
The crust formed in the early stages of Earth's development has a higher abundance of gold. Therefore, largely representative of the early residual crust composition of the aeolian greenstone belt. Especially magnesium-iron and super magnesium-iron volcanic rock assemblage, gold abundance value is higher than the crust of various types of rocks, may become the earliest gold deposits "source layer".
Gold in the earth, the earth's core for 2.6 × 10-6, the mantle for 0.005 × 10-6, the crust for 0.004 × 10-6. Gold in the crust of the abundance of only iron 1/1 million, silver 1/21. 99% of the earth's gold into the earth's core.
In summary, the abundance of gold in the earth's crust is originally very low, and has a pro-sulfur, pro-copper, pro-iron high melting point and other properties. To form industrial deposits, gold to be enriched thousands of times to form large mines, rich mines, gold to be enriched thousands, tens of thousands of times, or even higher.
It is generally believed that the huge scale of gold mines generally have to go through a fairly long geological period, through a variety of sources, geological tectonic evolution and multiple metallogenic effects superimposed on the formation of possible.
Baidu Encyclopedia-Gold Mining