Gems. The hardest mineral in nature The hardest stone

The modern science of geology knows thousands of the most diverse minerals and rocks. And someone who, and geologists know for sure which stone is the most durable in the world. Do you know the answer to this question? If not, be sure to read our article.

The strongest stone is...

Nature has created a huge number of different minerals. Some of them are so soft that they crumble in your hands. But others are not deformed even from the strongest blow. What is the hardest stone in nature? Let's figure it out.

If we talk exclusively about minerals, then the answer is obvious - it's a diamond. This natural formation is one of the forms of pure carbon, which is formed in the bowels of the Earth at considerable depths. The mineral is at the top with an absolute hardness of 1600 units. In addition, a diamond also has such a quality as metastability (that is, the ability to exist indefinitely for a long period of time under normal environmental conditions).

It is worth noting that the word "stone" can also mean such a concept as a rock (an aggregate of one or more types of minerals). It is not so easy to determine the absolute champion in hardness among rocks. Most often, the following rocks fall into the list of the most durable stones:

• Gabbro.
• Diabase.
• Granite.

Mineral diamond: basic properties

So, the most expensive, most desirable, most beautiful and most durable stone on Earth is a diamond. And it's hard to argue with that. However, the very name of this mineral is more than eloquent. The word "diamond" in translation from ancient Greek means "indestructible".

The first historical evidence of a transparent stone of unprecedented strength came to us from Ancient India and China. At the same time, the Indians called him fariy. But the Chinese, as early as the third millennium BC, used diamonds to grind their ceremonial axes made of corundum.

What are the physical and mechanical properties of the most durable stone in the world? Let's list the most important of them:

• Luster: diamond.
• Line color: no.
• Hardness: 10 (Mohs scale).
• Density: 3.47-3.55 g/cm 3 .
• Fracture: conchoidal to splintery.
• Syngony: cubic.
• Thermal conductivity: 900-2300 W/(m K) (very high).

The most common color of diamonds is yellow or colorless. Minerals of green, blue, red or black color are the least common in nature. Another important property of all diamonds is their ability to luminesce. Under the influence of sunlight, they begin to glow and shimmer in various colors and shades.

• Diamond, graphite and coal are all made up of the same element (carbon).
• On some planets of the solar system, it rains diamonds.
• Diamond cannot be called the rarest stone on Earth. There are at least ten gemstones that are much rarer in the earth's crust.
• The headquarters of the largest company for the extraction and processing of natural diamonds is located in Johannesburg (South Africa).
• Under certain conditions, diamonds can be synthesized from tequila or peanut butter.
• A beam of light passing through the body of this mineral reduces its speed by half.
• 80% of diamonds mined today are used for industrial purposes.

Major diamond deposits

Diamonds are formed at a depth of 80-150 kilometers under the influence of colossal pressure and temperature. Then, thanks to volcanic activity, they rise closer to the surface of our planet, thus forming vertical deposits - kimberlite pipes. This is how, for example, the neck of such a pipe looks like in Yakutia (diamond quarry "Mir"):

In addition, some diamonds may also be of meteoric origin. Such minerals are formed when a cosmic body contacts the Earth's surface. So, "extraterrestrial diamonds" were discovered in the Grand Canyon in the United States.

It so happened that the richest deposits of diamonds on Earth are concentrated in the depths of Africa. It is here that the largest mining company in the world, De Beers, is based. Diamonds are actively mined today in South Africa, Angola, Botswana, Namibia, Tanzania, Russia, Canada, and Australia. The leader of the Russian diamond industry is ALROSA.

The use of diamonds in industry

Do not think that diamonds are used exclusively in jewelry. The hardest stone is also widely used in industry. In particular, heavy-duty drills, knives, cutters and other products are produced from it. (in fact, the waste obtained during the processing of natural diamonds) is used as an abrasive in the production of grinding discs and circles.

Diamonds are also used in nuclear power engineering and quantum electronics. Another extremely promising area today is microelectronics on diamond substrates.

Hexagonal diamond

Ten years ago, a diamond could be counted on Earth. But in 2009, a group of scientists from China and the United States managed to prove the falsity of such a claim. According to them, the most durable substance in the world is an artificial material called lonsdaleite (or hexagonal diamond).

Using the method of computer simulation, scientists were able to establish that this material is 58% stronger than diamond. And if the latter collapses at a pressure of 97 gigapascals, then lonsdaleite is able to withstand loads of 152 gigapascals.

However, the hexagonal diamond exists so far only in theory. However, scientists doubt that the new material will ever be applied in practice. After all, the process of obtaining it is extremely complex and expensive.

The hardness of stones is determined by Mohs scratch hardness and Rosival hardness. Nowadays, only collectors and amateurs determine the hardness of stones on the Mohs scale. Previously, when optics was not yet highly developed, the method of determining scratch hardness determined the authenticity of precious stones. Now they have learned to grow stones artificially and therefore the Mohs method does not determine very accurately. The Viennese mineralogist Friedrich Moos came up with this method of determining hardness. This method has a drawback - you can damage the stone, but there are pluses, it does not require expensive equipment and a laboratory.
The principle of this method is to determine the resistance of a stone to scratching its surface with a sharp special object. Stones with a Mohs hardness above 7 are hard stones, and stones with a hardness below 7 are subject to abrasion by ordinary dust, since the dust contains tiny grains of quartz that have a Mohs hardness of 7. Therefore, stones with a Mohs hardness below 7 quickly fade, they are quickly erased polished and scratched heavily when in contact with harder objects. It is necessary to produce scratch hardness only with the sharp edge of the sample only on even and fresh stone surfaces, and if it is determined on ribbed formations or on pieces weathered from the surface, then the values ​​of scratch hardness will be underestimated. Some stones on different faces and on different planes may have different scratch hardness. For example, diamond has such differences and thanks to this it can be polished, although the hardness of diamond on the Mohs scale is considered the highest.
Below is a relative scale of Mohs hardness of stones, which shows how a stone can be scratched and what Rosival grinding hardness a stone has, depending on the Mohs scratch hardness.

Mohs scale table for easy determination of hardness

Having determined the hardness of the scratching of the stone, then it is possible to determine the conformity of the stone according to a specially created table.
Relative Mohs table.

The gem some time ago lost its title of the hardest material in the world, giving way to artificial nanomaterials of slightly greater hardness. Today, a rare natural substance is likely to leave everyone else behind - it is 58% harder than diamond.

Peng Zicheng (Zicheng Pan) from Shanghai Jiao Tong University, together with colleagues, modeled how atoms in two substances, supposedly having the properties of very hard materials, would respond to the impact of a special sensor.

Extreme conditions

The first - wurtzite boron nitride has a structure similar to diamond, but consists of other atoms.

The second, the mineral lonsdaleite, or hexagonal diamond, is made up of carbon atoms like diamond, but they are organized differently.
Simulations have shown that wurtzite boron nitride is able to withstand 18% more impact than diamond, and lonsdaleite 58% more. If the results are confirmed within the framework of physical experiments, both materials will be much harder than any known substance.

But it will not be easy to carry out such tests, because. both materials are not often found in nature.

The rare substance lonsdaleite is formed when meteorites containing graphite fall to Earth, and wurtzite boron nitride is formed during volcanic eruptions at high temperatures and pressures.

Flexibility

With successful results, wurtzite boron nitride may become the most applicable of the two, due to the fact that it is resistant to oxygen at higher temperatures than diamond. This makes it ideal for use on the ends of cutting and drilling tools operating at very high temperatures, or as corrosion resistant films on spacecraft surfaces, for example.

Paradoxically, wurtzite boron nitride owes its hardness to the flexibility of the bonds between the atoms that form it. When the material is stressed, some of the bonds change direction almost 90º to relieve stress. After diamond and wurtzite boron nitride were subjected to the same process, something in the structure of wurtzite boron nitride made it nearly 80% harder, says study co-author Changfeng Chen of the University of Nevada at Las Vegas.

Scientists emphasize that in order to prove the theory, single crystals of each of the materials are needed. At the moment, there is no way to isolate or grow such crystals.

To date, there is no single classification of semi-precious stones, there is only a conditional division. You can learn everything about stones, their description properties on the website http://www.catalogmineralov.ru/cont/poludragocennye_kamni.htm. When deciding to make a gift with a semi-precious stone to a loved one, first get acquainted with this stone.

What in inanimate nature delights and amazes people more than gems? Precious stones are amazingly beautiful and rare, their possession makes a person wiser and more majestic - in any case, so many legends and beliefs associated with these most beautiful minerals assure. But which stone is the most expensive in the world? We will find out the opinion of experts on the cost of the most expensive stones.

10 Emerald and sapphire

On average, a good sapphire (about 6000 per carat) turns out to be more expensive than a not very high-quality emerald. This, of course, applies to ordinary, blue or light blue, sapphire. As for the rarest orange gem (it is called padparadscha), we will talk about it ahead. It is definitely one of the most expensive stones in the world.

As for emeralds - stones of a dark green or grassy color - despite their relatively large number, there are very few pure specimens. They are the ones that are so highly valued.

There are a couple of amazing examples. Firstly, it is the Millennium - a 61 thousand carat sapphire, decorated with carvings - 134 portraits of the most prominent world celebrities of the millennium, including, for example, Beethoven, Shakespeare and Einstein. At the moment, its price is 180 million dollars.

And the largest emerald is the Bahian nugget, which weighs 1.9 million carats and costs $400 million.

This is the rarest red beryl, which is mined exclusively in the states of Utah and New Mexico in the United States. Only a few stones are known, of which the largest weighs just over 3 carats.

One carat costs at least 10 or even 12 thousand dollars. This is due not only to beauty, but also to the exceptional rarity of the gem.

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