Gold is a chemical element easily recognized by its yellow metallic colour. It is valuable because of its rarity, resistance to corrosion, a good conductor of electricity, malleability, ductility, and beauty. If you ask people where gold comes from, most will say you obtain it from a mine, pan for flakes in a stream, or extract it from seawater. But, how did it get there? How is gold formed?
All of the gold found on Earth came from the debris of dead stars. Yes, the process by which gold is created takes place amongst the stars and eventually finds its way to Earth over time.
There are two main theories about how gold is originally formed. One theory involves the explosion of supernova stars and the resulting nuclear fusion creating atoms of gold. The other is the collision of neutron stars that results in a gamma-ray burst, one of the most powerful explosions possible.
Then, how does gold get into the ground?
As the earth formed, heavy elements such as iron and gold sank toward the planet’s core. Then, around 4 billion years ago, Earth was bombarded by asteroid impacts. These impacts stirred the deeper layers of the planet and forced some gold into the mantle and crust.
That gold is then deposited in rock ore in a number of different forms, including: flakes, mixed with silver as electrum, or as the pure element itself. Over time, erosion frees gold from other rocks, and since gold is heavy it sinks to the bottom of river beds, the ocean, and the like. Similarly, earthquakes have a huge role in bringing gold to the surface. During quakes the fault will rapidly decompress the water that’s rich in minerals. That water will vaporize and leave veins of gold (and other things) deposited. Volcanoes perform a similar function!
Just how much gold is there then?
According to estimates, all of the gold ever mined in the history of humanity amounts to about 152,000 metric tons. This sounds like a lot, but it is only about enough to fill up 60 trailers. Scientists believe that there is still eight times more gold in and under the oceans than has ever been mined close to the earth’s surface. Like the gold that is probably floating in the Earth’s molten core, most of this supply of the precious metal is inaccessible or simply too expensive to mine. Interestingly, gold has been discovered on all of earth’s continents except for Antarctica. Of course, it is possible that even that continent holds some gold under all of the ice.
How is gold processed?
Once the gold has been found and mined from its source, whether that’s a dedicated goldmine or not, it needs to be processed to become ready for use in gold jewelry. Gold can be recovered from ore in a few ways.
These include amalgamation and cyanidation. Cyanidation is the most popular and involves oxidizing and dissolving gold in alkaline cyanide and separating the resulting gold solution from the solids. It then has to be refined by removing all the impurities in the substance, which involves either melting and treating it with gas chlorine or using electrolysis. It is then tested for purity with 99.9% purity used as the benchmark.
Once gold has been processed and refined, it’s ready for use in whatever product, whether that’s electronics, dentistry, aerospace, or any of the other applications for gold.
However, processed gold has a range of qualities that make it particularly perfect for jewellery, including malleability, rich colouring, and shininess.
Can’t scientists make gold?
Believe it or not, scientists have found the ability to create gold from other elements. But making gold isn’t as simple as directly adding or subtracting protons from other elements. The process requires nuclear reactions that are similar to the r-process in stars.
The most common method of changing one element into another (transmutation) is to add neutrons to another element. Neutrons change the isotope of an element, potentially making the atoms unstable enough to break apart via radioactive decay.
Japanese physicist Hantaro Nagaoka first synthesized gold by bombarding mercury with neutrons in 1924. While transmuting mercury into gold is easiest, gold can be made from other elements—even lead! Soviet scientists accidentally turned the lead shielding of a nuclear reactor into gold in 1972 and Glenn Seabord transmuted a trace of gold from lead in 1980.
But all of those methods are prohibitively expensive and impractical to produce and sell for their current uses.