In October 2021, geological prospectors discovered a gold deposit in Tongbai County, Henan Province, with an estimated reserve of about 31.55 tons, which is a very large gold mine. When the news came out, everyone cheered, as if they had seen a golden mountain.
How much is 31.55 tons of gold? Many friends don't have a concept. Gold is a heavy metal, it is heavier than most common metals, at room temperature density of 19.32 g / cm3, 31.55 tons of gold volume is about 1.18 meters long cube. According to the recent international transaction price of 370 yuan / g, if the gold found in Henan is all mined at no cost today, it is worth about 11.67 billion yuan, far from enough to repay Evergrande's debts.
31.5 tons of gold is probably that much
China is currently the world's largest annual output of gold, in 2020 gold mineral gold 301.69 tons, through metal smelting by-products to extract gold 63.65 tons, a total of about 365 tons; of which Henan mineral gold 35.24 tons, smelting and extraction of gold 67.94 tons, after Shandong, is China's second largest gold producing province.
However, mining gold is not easy and the cost is very, very high. Many people imagine a gold mine like this:
Zimbabwe gold mine
This is a gold mine in Zimbabwe, and the golden light in the mine is actually the illusion of refraction of light by quartz and iron sulfide. Although there are occasional underground hydrothermal streams that create veins rich in gold, and some people are lucky enough to dig up "dog head gold", in the vast majority of gold mines, we can't see gold with the naked eye.
Gold veins and ores
There is not much gold on Earth, and more than 99% of it is buried deep in the earth's core. By analyzing the iron meteorites that fell to the ground, astronomers found that the iron and nickel composition inside was similar to the composition of the Earth's core, proving that these iron meteorites were once fragments of the core of the original planets in the solar system. In addition to iron and nickel, iron meteorites contain a small amount of other heavy metal elements, of which the gold content is about two parts per million.
Considering that the core of the earth is 2442 kilometers in diameter and a total mass of 19 trillion tons, gold is a ferrophilic metal, it is easily dissolved with iron, so according to the same proportion, the gold in the core of the earth should be no less than 3800 trillion tons!
Gold was produced by supernova explosions or neutron star mergers tens of billions of years ago, and under great pressure, small metal nuclei were pressed into larger and heavier nuclei, resulting in several earth-mass heavy metal elements such as gold, silver, platinum, and uranium. When the solar system formed, heavy elements gathered closer to the Sun, so there was gold on Mercury, Venus, and Earth. The earth was very hot at the beginning of its formation, it was like a magma ball, and heavy metals such as iron and nickel slowly sank to the core of the earth, and the gold on the surface became particularly rare. As the Earth slowly cooled, its crust hardened, and new stardust and asteroids fell to the ground and did not sink, forming the metal deposits we see today.
Gold is not visible in most gold ores
However, the gold falling from the sky is extremely scattered, and even the iron meteorite with the highest gold content contains only 2 grams of gold in 1 ton, which is really pitiful. As we said earlier, real gold ores, you may not be able to see gold, the gold inside is only a very small particle, they are mixed in the crevices of sedimentary rock, or other minerals, you need to know through chemical methods to know whether there is gold in it.
There are many high-grade gold mines in the world belonging to the Carlin type of gold, due to the change and extrusion of the earth's crust, a part of the gold-containing sedimentary rock is turned into lava in the depths of the earth's crust, gold is gathered in the lava, and then with the volcanic eruption or magmatic movement is squeezed to the surface, so that some gold-rich deposits are formed.
Natural Gold, Sand Gold and Dog Head Gold
Some of the gold deposits exposed to the surface are weathered and broken, and the gold is buried in the sediment, and those large pieces of natural gold are called "dog head gold".
The earliest metal on Earth to be discovered and utilized by humans is gold, and archaeologists have found natural gold particles collected by ancients in Paleolithic caves in Spain; in 4000 BC, gold products were popular in ancient Egypt. Because of its softness, it was most easily made into various ornaments and totems by the ancients with simple tools. After thousands of years of mining, there are fewer and fewer high-grade riches, and people have to sift and smelt precious metals from lower gold-content ores.
Today, geologists choose early geologically active areas for prospecting in an attempt to find traces of gold. The cost of prospecting is very high, even if it is speculated from the law of crustal activity that there may be precious metal deposits in a certain area, people still need to drill a large number of holes to extract the core, and then analyze the chemical composition of the rock through chemical methods to determine whether it is worth mining.
Gold exploration is expensive
Some gold mines are buried tens to hundreds of meters deep underground, and all processes such as digging mines, transporting ore, crushing, screening, separating, extracting, and purifying all cost very high. If 1 ton of hard rock contains less than 1 gram of gold and there are no other valuable metals, the mining value of this gold mine is not large, because the cost is already higher than the market price of gold, and one gram is lost.
Although henan's newly discovered gold reserves are comparable to the total production of gold in 2020, it takes more than ten or even decades to fully mine the 31.55 tons of gold, considering the cost of exploration, mining, and environmental remediation costs after mineral processing extraction, the pulling effect of tens of billions of gold on the economy is still relatively limited.
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