How has gold formed and evolved over the years?
How do you explain the origin of gold?
Gold is part of our everyday lives: it’s in our jewelry, our works of art and our electronic components. But do you know where this precious metal comes from? The formation of gold is not terrestrial: it is thought to have taken place over 4 billion years ago, during the explosions of stars! In this article, we take a look at the origins of gold, which are extraterrestrial.
The first hypothesis concerning the origin of gold is that of an explosion of massive stars (called supernovas). Their nuclei are made up of hydrogen, a simple, light chemical element. But the gravitational pressure is such that it compresses the core, triggering nuclear fusion.
This fusion process has been going on for millions of years. Hydrogen molecules are gradually transformed into heavier chemical elements such as helium, carbon and oxygen. These are then consumed and transformed into metals such as iron and nickel.
Eventually, the pressure in the core is exhausted and the star collapses in on itself. In the process, it generates an astronomical amount of energy and explodes into a supernova. The extreme pressure causes protons and electrons to combine to create neutrons. These are then absorbed by ferrous elements, giving rise to lead, uranium, silver and… gold!
The transformation of hydrogen into helium takes millions of years, but it only takes a few seconds to create gold in a supernova. The star’s explosion produces a shockwave, hurling debris and heavy metals into the cosmos. This vortex then condenses into new stars and planets.
The first hypothesis concerning the origin of gold is that of an explosion of massive stars (called supernovas). Their nuclei are made up of hydrogen, a simple, light chemical element. But the gravitational pressure is such that it compresses the core, triggering nuclear fusion.
This fusion process has been going on for millions of years. Hydrogen molecules are gradually transformed into heavier chemical elements such as helium, carbon and oxygen. These are then consumed and transformed into metals such as iron and nickel.
Eventually, the pressure in the core is exhausted and the star collapses in on itself. In the process, it generates an astronomical amount of energy and explodes into a supernova. The extreme pressure causes protons and electrons to combine to create neutrons. These are then absorbed by ferrous elements, giving rise to lead, uranium, silver and… gold!
The transformation of hydrogen into helium takes millions of years, but it only takes a few seconds to create gold in a supernova. The star’s explosion produces a shockwave, hurling debris and heavy metals into the cosmos. This vortex then condenses into new stars and planets.
The origin of gold also fits a second theory developed by Edo Berger, a professor of astronomy at Harvard University. In 2013, he put forward the idea that a cataclysmic collision between two neutron stars could be the cause of gold’s formation.
This involves a violent collision between two neutron stars, which triggers nuclear reactions enabling the instant formation of gold and other heavy metals. Each time, the quantity of gold produced would be equivalent to 10 times the mass of the Moon.
Today, buying and selling gold is an integral part of our daily lives. But where does it actually come from?
Over thousands of years, gold from the stars has spread to Earth in the form of deposits. Our planet’s geothermal activity allows these deposits to circulate beneath the earth’s crust, and the transported metals are gradually deposited in the form of veins. The precious yellow metal is then collected by mining or in rivers.
It’s worth noting that ⅔ of annual gold production is achieved by 10 producing countries. Since 2007, China has been the world’s leading gold producer, producing almost 400 tonnes of gold every year. The next largest producers are :
- Australia;
- Russia;
- South Africa;
- United States;
- Canada ;
- Peru ;
- Ghana ;
- Mexico.
Gold deposits are therefore found all over the world and on every continent. Unlike hydrocarbons, gold is not concentrated in certain regions. The presence of more gold in certain areas of the Earth’s surface can be explained :
- the impact of gold-bearing meteorites around 4 billion years ago;
- by the presence of a form of sulfur in the earth’s crust, the trisulfide ion S3, which allows gold to be easily transported.
As we discovered earlier in this article, the origins of gold and heavy metals lie in extreme and exceptional conditions. Hence their rarity!
Gold is only available in low concentrations in the earth’s crust: there are between 163,000 and 166,000 tonnes of gold above the surface, which works out at around 20 grams per person if you had to divide it up.
The average gold content per tonne of terrestrial rock is 1 milligram. This makes it one of the rarest metals on Earth. And it is estimated that since the beginning of mankind, all the gold extracted represents 171,300 tonnes: the equivalent of a cube about 20.7 metres on a side.
Can gold be made artificially?
Insofar as gold is used as currency and still plays an important role in our monetary system, the question arises as to whether it is possible to artificially manufacture this rare metal to avoid a shortage.
The gold we find today in mines therefore comes from a phenomenon of exploding stars that has not been reproduced in billions of years. But many chemists have turned their attention to gold to find a way to manufacture this precious metal.
Today, no method is yet known and approved for synthesizing gold. Artificially, the quality of gold cannot be found in gold coins, ingots or even gold jewelry. Scientists did manage to generate synthetic gold, but it was radioactive. To do this, a mercury atom is bombarded with a fast neutron in a particle gas pedal: this produces a gold atom after a few successive reactions.
Insofar as gold is used as a currency and still plays an important role in our monetary system, the question arises as to whether it is possible to artificially manufacture this rare metal to avoid a shortage.
The gold we find today in mines therefore comes from a phenomenon of exploding stars that has not been reproduced in billions of years. But many chemists have turned their attention to gold to find a way to manufacture this precious metal.
Today, no method is yet known and approved for synthesizing gold. Scientists did manage to generate synthetic gold, but it was radioactive. To do this, a mercury atom must be bombarded with a fast neutron in a particle gas pedal: this produces a gold atom after a few successive reactions.
But for just one gram of gold, the neutron-emitting reactor has to be operated for almost 4 days. And to transform mercury nuclei into gold, it would take 58 days! Using nuclear energy is too costly, not to mention that the result is not yet viable.
Today, scientists are looking at bacteria such as Metallidurans Cupriavidusles, which are capable of transforming gold chloride into 99.9% pure, solid gold. This process, known as gold biomineralization, is promising but far from generalizable, since no less than 200,000 cubic meters of water are needed to obtain one kilogram of 24-carat gold.
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