Some metals are simply “scarce”, other metallic elements are very difficult to find and obtain. At the same time, we cannot do without them. Where did gold come from, where to look for such a rare metal and, above all, how to find it?
Gold. Latin aurum. One of the first rare metals we learn about in our lives and hear about every now and then. Does that make it seem “normal” to you? Its origin is certainly not. According to scientists, gold is one of the products of the collision of two neutron stars.
The energy released by the collision was enough to fuse the protons and neutrons into a heavy gold atom. The dust that was scattered through space contained gold, and the same dust was part of the matter from which the Solar System, including the Earth, began to form about 4.7 billion years ago.
Surface gold
Most of the gold as well as iron and platinum existing in the early phase of the Earth apparently “sunk” into the planetary core. Still, there is more gold at the surface than experts say there should be.
The largest gold mines in the world •
Profimedia.cz
According to research by scientists at the University of Bristol, these reserves are the result of a meteoric “bombardment” of the Earth that broke out several hundred million years after its formation. The falling bodies were supposed to contain a large amount of gold, platinum and other precious metals, which at the same time did not sink into the depths of the planet.
But there is one catch – gold and platinum are strongly siderophilic elements. This means that, together with meteoritic iron, they should not remain on the surface, but should descend through the Earth’s crust and collect almost exclusively in the Earth’s core. What with this?
Mysterious layer
A team of Jun Korenaga of Yale University and Simone Marchi of the SRI Research Institute in Colorado recently came up with a possible answer. Their study focused on a thin and almost non-existent layer of the earth’s mantle, which was formed after the collision of large bodies with the early Earth.
The shallow part of the mantle melted and the deeper part remained solid. Due to its properties (it was actually an “ocean of lava”), the layer captures the falling metal components and gradually transports them to the rest of the mantle.
According to experts, the remnants of the area are still observable as anomalies in the current earth’s mantle. That’s where we find gold. And although the peculiar dynamic appeared for a short period of time billions of years ago, its influence lasted for an extremely long time.
Mining continues
Regarding gold and other precious metals, we have to make do with what we have. According to the US government agency US Geological Survey, there were still about 50,000 tons of gold left 5 years ago. According to expert estimates, roughly 209,000 tons have been mined throughout history. More than 3,000 tons of gold have been mined annually worldwide in recent years. The world leaders in mining are China, where 332 tons of gold were mined the year before, and over three hundred tons were also mined in Russia and Australia.
A gold nugget, i.e. gold in its purest form as found in nature •
Gump Stump, CC BYSA 3.0, Wikipedia
Golden water
But there are stores of precious metals, including gold, that have not yet been touched by human hands – on the bottom of the oceans. For example, in the Atlantic Ocean and the Northeast Pacific, the occurrence of gold is roughly 10 to 30 grams per square kilometer.
However, efficient marine gold mining is not yet possible. There are two reasons for this. On the one hand, it is financially demanding and not worth it, and then more than half of the area of the ocean floor is protected by a special international convention, which states that it is a common civilizational heritage and must not be mined there. But in recent years, there have been attempts and plans for deep-sea mining of gold and other precious metals.
Gold and other precious metals were formed before the Earth was formed during the collision of neutron stars •
Gump Stump, CC BYSA 3.0, Wikipedia
Highly sought after, elusive
In addition to rare metals, there are so-called rare earths, or rare earth metals. There are 17 elements – scandium, yttrium and a 15-member group of so-called lathanoids. The rarest are neodymium, praseodymium, terbium and dysprosium, which serve as miniature super-strong magnets. We can find them in mobile phones, but also in electric car batteries or wind turbines.
They are hard to find
At the same time, these elements are not that few in the earth’s crust. However, they are difficult to mine. “The problem is that they are simply not concentrated in one place. All the shale in the United States has about 300 milligrams of rare earths per kilogram,” Paul Ziemkiewicz, director of the West Virginia Water Research Institute, told Live Science magazine.
Metals are usually concentrated in various places in the earth’s crust due to geological processes, for example lava flows or the formation of mountains. But rare earth elements are usually not collected, and their extraction is therefore difficult and inefficient.
Machines being prepared for mining at a depth of 1,600 meters, from which the launch into action finally failed •
Gump Stump, CC BYSA 3.0, Wikipedia
Too much effort?
Rare earth metals are extremely difficult to separate from rock. Therefore, for the separation, it is necessary to overcome the extremely strong attraction between the positive metal and the negative phosphate, which requires a lot of energy and chemicals.
“This process often uses very low pH, very aggressive conditions, and very high temperatures because these bonds that hold the ores together are very strong,” explained Aaron Nobel of Virginia Tech. In short, we can say that these elements are not very rare, but rather “very problematic”. But modern society cannot do without them, at least for now.
Dirty Gold:
Mining destroys nature
However, gold mining also has a bitter aftertaste. Seven percent of annual gold production is obtained illegally, and for 25 percent, it is uncertain whether it was mined according to the law. Gold mining is also very demanding on the consumption of water and has serious ecological impacts – it is associated with the production of toxic mercury, greenhouse gases and other dangerous substances and has a direct destructive effect on the landscapes in which it is mined.
