California’s Gold Rush

It happened on 24 January last year in a sawmill on the American River: During construction work on a sawmill, James Wilson Marshall discovered a gold nugget. Although attempts were made to keep the find a secret, the story quickly got around: there is gold on the American River!

Soon the first gold prospectors from all over California crowded to the river. Thousands of workers in San Francisco threw down their jobs and came to make their fortune on the riverbank. But it was not only the inhabitants of the country who were gripped by gold fever. More than 50,000 people from Mexico, Chile, China and above all Europe flocked to California and flooded the cities here. San Francisco in particular was bursting at the seams by the migration. In just one year since the discovery of the first gold nugget, the Californian population has now grown fivefold.

The hopes of the immigrants are high, the yield from gold panning often low. Although, with a bit of luck, much more can be earned here than a worker receives as wages on the East Coast, life in the gold-mining sites is expensive. Simple foodstuffs have to be bought at exorbitant prices. An egg costs a dollar, a newspaper even ten! On top of that, some prospectors blow their new wealth on gambling or alcohol in the saloons. For some, the gold rush has already ended with a nasty hangover.

Washing gold – how does it work?

The technique of the Californian gold prospectors is simple: the search does not require much more than a tin pan and a leather bag. You shovel sand and silt from the river into the pan. When you swirl the pan, water and sand are flushed to the edge. Now it gets exciting: with a lot of luck, small pieces of gold flash at the bottom of the pan. Because they are heavier than the rest, they remain in the middle. The gold pieces can be collected in a leather bag and the next pan is next. Good luck!

Largest diamond ever found!

A rough diamond larger than any known diamond on earth was found in a South African mine on Thursday. This record-breaking gemstone weighs in at 3106 carats. It was discovered by Frederick Wells, the mine’s inspector.

It happened late in the afternoon during a routine inspection at the Premier Mine near Pretoria. On his tour of the mine, Frederick Wells saw something light up above him. Wells became curious and looked closer. Could the shimmering thing really be a huge diamond? He managed to detach the stone from the wall and still wasn’t sure if it wasn’t a piece of glass that was fooling him. Investigations, however, could prove that he was really dealing with a diamond. And the largest one ever discovered on earth at that. The precious lump has exactly 3106.75 carats. That corresponds to a weight of 621.35 grams or a little more than 6 bars of chocolate.

Frederick Wells is now to receive a “finder’s reward” of 10,000 dollars for his sensational discovery. The largest diamond of all time will be named after mine owner Sir Thomas Cullinan: the famous “Cullinan Diamond” is already being talked about everywhere.

The “imperishable

Its sparkle has driven many a person out of their mind – or at least out of a fortune. No wonder, because the diamond is the most valuable of all gemstones. And not only that: it is the hardest known mineral. That is why this dazzling gem is also called “the imperishable”. Legends and myths surround this rare jewel. Famous diamonds such as the “Hope” or the “Florentine” are even said to be cursed, bringing misfortune and death to their owners. For others, however, the diamond is a symbol of eternal love, wealth and power.

Gemstones

Whether green emerald, blue sapphire or red ruby: we know gemstones as sparkling and particularly valuable pieces of jewellery. Yet gemstones are simply minerals. However, they have to fulfil three conditions to be considered precious stones: They must be particularly rare, transparent and at the same time very hard.

Gemstones are formed deep inside the earth under high pressure and at high temperatures. The hardest among them and at the same time the hardest known mineral is the diamond. It forms at a depth of about 150 kilometres at temperatures of over 1200 degrees Celsius from a single element: carbon. In the process, crystals develop from mostly eight equilateral triangles, called octahedrons. Other shapes such as cubes are also possible. The diamond comes to the earth’s surface by being thrown upwards together with rising magma. The largest diamond ever found is the so-called “Cullinan”. It was discovered in 1905 in a South African mine and weighed exactly 3106.75 carats in its rough state. This corresponds to a weight of 621.35 grams.

Whether diamond, amethyst, emerald or topaz – all gemstones differ from each other in structure, composition and colour. They all only become particularly beautiful and shiny through the cut. It makes the colours of the gemstones really shine through a certain refraction of light.

In addition to gemstones, other gemstones such as blue lapis lazuli or green malachite are found in the earth’s crust. While these are also highly sought after and beautiful, they are not transparent and are too common to be considered gemstones.

From the bowels of the earth: ores and dignified metals

Copper was the first metal that man discovered in the earth’s crust. It could be formed into simple tools or weapons and was so important that an entire era was named after it: the Copper Age. The tools got better when man mixed the copper with tin and thus invented bronze. And when he learned to smelt iron, the triumph of metal tools finally began.

Unlike the Earth’s core, the Earth’s crust consists largely of non-metals. Nevertheless, metals such as iron, aluminium, manganese or potassium can be found in its rock. Experts (geochemists) can determine exactly how often they occur. They have found out, for example, that about seven per cent of the earth’s crust consists of iron.

Like most metals, iron occurs as a chemical compound with other elements, as so-called ore. To extract iron from ore rock, the ore rock is ground, mixed with coal and heated. A chemical reaction then takes place that removes the other elements from the ore, leaving the pure, elemental iron.

Some metals, on the other hand, hardly combine with other elements. They therefore do not weather and occur in the earth’s crust in pure form. These “solid metals” include gold, silver or platinum. Platinum and gold are also extremely rare: On average, only 0.001 grams of gold is contained in one tonne of rock. However, a place is only called a deposit when it contains a thousand times the amount of gold – i.e. one gram of gold per tonne of rock.

More common than gold or platinum are the “rare earth metals”. What sounds strange has a simple reason: These metals are considered rare because they do not form their own deposits, i.e. they do not occur in concentrations but only in scattered form. This is why we also talk about spice metals. Their importance has increased greatly in recent years because they are needed for the production of electronic devices such as mobile phones or computers.

From rock to grain of sand – weathering

Today, northern Canada is a gently undulating landscape. Many millions of years ago, however, a mountain range stood here. In fact, over a very long time, even high mountains can turn into small hills.

The reason for this transformation: the rock on the earth’s surface is constantly exposed to wind and weather. If, for example, water penetrates into cracks in the rock and freezes, it blasts the stone apart. This process is called frost blasting. Changes in temperature between day and night and the force of water and wind also cause the rock to become friable. In other words, it weathers. This process can also be observed on buildings or stone figures. During weathering, the rock breaks down into smaller and smaller components down to fine grains of sand and dust. Different rocks weather at different rates: granite, for example, is much more resistant than the comparatively loose sandstone.

Some types of rock even dissolve completely when they come into contact with water, for example rock salt and lime. Rock salt is chemically the same as table salt – and that already dissolves in ordinary water. Lime is somewhat more resistant, but limestone also dissolves in acidic water. Acid is formed, for example, when rainwater in the air reacts with the gas carbon dioxide. This “acid rain” attacks the limestone and dissolves it over time. On the earth’s surface, weathering leaves behind fissured limestone landscapes, while caves form underground.

But it is not only solution weathering, but also heat and pressure that wear down and crumble rock beneath the earth’s surface. Where plants grow, roots dig in, blast the rock apart piece by piece and also ensure that it is eroded millimetre by millimetre.

The outermost shell of the earth

Like an egg from an eggshell, the Earth is also surrounded by a hard shell. This outermost layer surrounds the Earth’s mantle and is called the Earth’s crust. If you compare the earth to a peach, the earth’s crust is – relatively speaking – as thick as its skin. Under continents, it reaches an average depth of 40 kilometres, under the oceans even only about seven kilometres.

Below this lies the outer part of the Earth’s mantle, which reaches down to a depth of about 100 kilometres. It is also solid, but consists of heavier rock. The earth’s crust and this outermost part of the mantle together are also called the “lithosphere”. This solid layer of rock is broken into plates of different sizes that drift very slowly on the hot, viscous mantle.

Where the molten rock from the hot mantle penetrates upwards, the earth’s crust can break open. Lava then flows out and becomes new crust. This mainly happens where the plates of the lithosphere adjoin each other, such as at the mid-ocean ridges.

In Iceland, for example, these plate boundaries are clearly visible: Cracks and furrows run through the earth’s crust here, where the Eurasian and North American plates drift away from each other. There is also a plate boundary in the Mediterranean region. Because the African plate is pressing against the Eurasian plate here, there are many volcanoes and earthquakes in Italy.

The crust is covered by the soil. The soil of the land masses forms from weathered rock and the remains of animals and plants. The seabed, on the other hand, develops from deposits such as clay and the sunken remains of marine organisms. On the coasts, the seabed also consists of deposited debris that has been eroded from the mainland and washed into the sea.

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Plants rarely grow on bare rock. They need a soil from which they can draw nutrients and in which they can form roots. For such soil to develop, weathering is necessary: rain and oxygen, heat and cold, water and wind grind the rock and thus grind even hard granite into smaller and smaller grains. What emerges is the so-called weathering debris.

But thousands of years pass before it becomes living soil. Bacteria, fungi and lichens are the first to settle on the rock; the first soil animals are attracted to them. Dead plant remains, animal carcasses and faeces gradually mix with the crushed rock. From this mix, with the help of fungi and bacteria, the upper soil layer of fertile soil develops, on which plants can thrive. Below that are other layers, for example of sand or clay. At the very bottom is the rock from which the soil develops.

Depending on which rock is weathered, how wet it is, which plants grow and what temperatures prevail, different soils with different properties and colours are created. Whether weathered rock is washed away or deposited also plays a role.

In our temperate latitudes, brown earths are common. They develop on rock with little or no limestone in a humid climate. Dark coloured is the rendzina, a soil that forms on limestone. Because it is so stony, it is difficult to cultivate crops on it. And on the Italian island of Stromboli there are very special sandy soils: because the lava rock that comes from the Stromboli volcano is dark, the sandy beaches on the volcanic island are also pitch black.