Gold, precious stones, minerals: this is how the treasures in the earth are created |

Hundreds of kilometers below the earth’s crust, the solid surface on which our life takes place, nature operates a huge chemistry laboratory. At this depth it is incredibly hot and there is incredible pressure. Here the rock deforms and liquefies. Crystals, precious stones and metals such as copper, gold and silver are created here over millions of years.

Gemstones and Minerals – How Are They Made?

In order to understand how minerals, gemstones, metals or crystals are created and what happens inside the earth, the processes in the depths of the earth are simulated in the laboratory at the Bavarian Geoinstitute in Bayreuth. For this purpose, the smallest capsules, which are no larger than a match, are filled with minerals.

They are pressed together using high-pressure equipment at temperatures of around 800 degrees Celsius with a pressure of up to 5,000 tons. The melt under these conditions allows rock to be broken down into its constituent parts and to investigate how much copper and gold it contains and what happens when the metals are enriched with sulfur or chlorine.

Copper is rare, but it is often used

Whether precious metals can be extracted also depends on the processes in the earth’s interior. Example: copper. In everyday life we ​​encounter it from pennies to gutters. Because of its electrical conductivity, it is used in computers, power lines and in the automotive industry. But copper is an extremely rare component in the earth’s crust.

This is how copper and gold are created in the earth’s interior

Gold nuggets are larger pieces of gold that are contained in gold veins in the quartz.  These were found on the Seward Peninsula in Alaska.  |  Image: picture-alliance / dpa

Gold nuggets from Alaska – a traditional gold rush country.

Where copper is found depends on the process of rock melting inside the earth: At high pressure and high temperature, the rock boils together to form a viscous melt, known as magma. This magma contains traces of water that evaporates. Certain tiny trace elements, such as copper, are extracted from the magma by the steam and various chemical processes and then accumulate in fine cracks and large crevices. These are then the so-called “veins”. Something similar happens with gold: The metal is deposited in strands of quartz in fine lenses and large nuggets. These metal treasures lie hundreds of kilometers deep. Before humans can reach them, nature has to help again.

Where gold is mined in Bavaria

It depends on heat and trace elements

Which metal is extracted from the magma depends, among other things, on how hot it is in the underground “pressure cooker” and which trace elements, salts, crystals and so on can still be found. Copper accumulates, for example, when dissolved table salt, chloride, is involved. When it comes to gold, the sulfur compounds in the earth’s interior are important.

The special thing about silver

In the upper areas of the earth’s crust, the silver ore is located in ore veins. Silver mining was the first to begin at the beginning of the 16th century, as the metal was not deeply stored. As an element in the periodic table, silver is located below copper and above gold. These elements are relatively soft metals, easy to shape – which is used in jewelry making – but they have a relatively high density.

A silversmith from Laos engraves a silver plate with a hammer and nail.  Silver is a relatively soft metal, but it has a high density.  |  Image: picture-alliance / dpa

Silver is a popular metal used to make jewelry and implements. Because it’s not that hard, it’s easy to engrave.

Silver has one of the highest electrical conductivities of all elements and the highest thermal conductivity of all metals. It reflects 95.5 percent of light, also more than any other metal, and is therefore used in the manufacture of mirrors. Since silver – like gold – hardly enters into chemical compounds, it is a precious metal, although not quite as precious as gold and platinum.

This is how a mineral becomes a crystal

Crystals are also formed in the earth’s interior: Atoms and molecules form crystal lattices – if these are perfect from the inside out, a perfect crystal such as pyrite can also arise, in which iron and sulfur are deposited in a ratio of 1: 1. This results in a perfect cube shape that is already laid out in the crystal lattice.

In order for a mineral to become a crystal, the optimal conditions for its growth must exist. Quartz turns into rock crystal when the appropriate temperature prevails and there is enough space. If the quartz, chemically silicon dioxide (SiO2), is cramped, it remains a simple white lump. But if the crystallization nucleus has enough space around it, the typical, pencil-shaped tips of the rock crystals slowly form. Chemically it remains a quartz, but because of its perfect exterior, it has become a crystal. So a crystal is nothing more than a perfectly grown mineral.

A gem has to be hard

The hardness of a gemstone makes it a gemstone. One starts with either its scratch hardness according to Mohs or its absolute grinding hardness. The scratch hardness is named after the German mineralogist Friedrich Mohs, who introduced it. This scratch hardness is understood as the resistance that a mineral offers when scratching with a sharp-edged object. The table is divided from 1 – 10:

1 Talk Can be scraped with a fingernail
2 Cast scratchable with fingernail
3 Calcit scratchable with copper coin
4 Fluorit easily scratchable with a knife
5 Apatit, Türkis, Lapislazuli still scratchable with a knife
6 Orthoklas, Titan scratchable with steel file
7 Quartz, amethyst scratches window glass
8 Topas scratches quartz
9 Corundum, ruby, sapphire ritzt Topas
10 Diamond scratches corundum

The diamond is the hardest gemstone

In order for a gemstone to be called a gem, it must have a hardness of 7. The diamond has a hardness of 10 and is considered to be the hardest. In addition to the hardness of a gemstone, it is also important that it has a special color, clarity and exceptional shine. The rarer it is then to be found, the more expensive it becomes.

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