PRECIOUS STONES
DIAMOND
Diamond- a type of crystalline carbon, hardness -10 on the Mohs scale (the hardest stone); Due to the peculiarities of the internal structure of the stone, a strong splitting of light occurs inside the stone, providing an unsurpassed “game” (irization). The best cut option is the classic diamond cut (KR-57).
A diamond is a cut diamond. Diamonds have been known to people for about five thousand years. The Arabs called it “almas” - the hardest. The Greeks gave him the name “adamas”, which translated means irresistible, indestructible.
Diamond is the most valuable among all jewelry stones. Not a single gem can compare with it in the brightness of its shine and the play of all the colors of the rainbow. Moreover, this property is preserved even if the ring or earrings with diamonds have not been cleaned for a long time. The high price is explained by the rarity and exceptional complexity of the cut. According to an old belief, cutting should not be abandoned for a long time and the work should not be passed on to each other, as the quality will be much worse.
Completely colorless (pure water) or slightly bluish varieties are highly valued. Unfortunately, most diamonds have faint yellowish, brownish and other colors that reduce their value. There are blue, pink, red, green, yellow, orange, blue and black diamonds.
The largest diamond found is the Cullinan, the Orlov diamond with a greenish-blue tint crowns the royal scepter of Russia. The magnificent Hope Diamond weighs only 45.5 carats and has a rare sapphire blue color. Today it is the most expensive small object in the world, each carat is worth about $5 million!
In 2000, a unique organization was created - the Kimberley Process, the goal of which is to fight for the “purity” of the origin of diamonds. Each participating country that mines and purchases them can only trade if they have a Kimberley certificate confirming the legal origin of the stones.
A common misconception is that cubic zirconia (cubic zirconia) is an artificial diamond. However, this is not true; cubic zirconia is an artificial crystal, most often used as a diamond substitute. And the technology for creating artificial diamonds is so complex that the jewelry obtained in this way will be three times more expensive than a natural one.
RUBY 
Ruby- a transparent variety of corundum, and thanks to the admixture of chromium, the stone sparkles with a deep red color. Hardness on the Mohs scale is 9 points. The palette of the gem is very diverse, ranging from light pink to deep red. There are rubies that combine blue and red colors, which gives a lilac or violet color. Sometimes the stone contains inclusions of the mineral rutile, which gives it a silky, pearlescent sheen and an asterism effect.
Ruby is one of the four most expensive jewelry stones. In terms of hardness, it is second only to diamond, and star-shaped crystals are valued more than diamonds. Such varieties are amazingly beautiful - in the center there is a bright sparkling point, from which six flickering rays radiate across the surface. Among rubies, the shade of piercing red with a violet tint, called “pigeon’s blood,” also stands out for its charm and value. Traditionally, the most valuable stones are deep red, with a slight purple tint.
Large crystals are found in nature much less frequently than similar diamonds: the largest known jewelry ruby weighed 400 carats, three stones were cut from it. The cost of natural ruby is very high, and not everyone can afford it. But a synthetic crystal is available to many admirers of beautiful stones, thanks to the French chemist A.E. Alexander, who created an artificial ruby in his laboratory in 1910.
In an ancient Indian treatise, two thousand years before the birth of Christ, he is called the “king of precious stones.” In Burma, where the best rubies in the world have been mined since ancient times, they believe that it brings invulnerability, but for this it had to be worn without taking it off, so that it becomes, as it were, part of the owner’s body, after which the owner can not be afraid of either a spear, or a sword, or arrows. The Burmese firmly believe that the national hero of Burma, Aung San, who never parted with a ruby, was killed by terrorists, having for the first time forgotten his amulet in the bathroom that day.
The largest known ruby, the Raja Ratna, weighs almost half a kilogram (2475 carats) and belongs to a modest Indian lawyer who inherited it.
In the old days, almost all red gems were called rubies, and many famous ones turned out to be noble spinels, garnets, and tourmalines. Thus, a red stone the size of a pigeon egg (250 carats), which the Swedish king Gustav Adolf III presented to Empress Catherine II as a ruby, turned out to be pink tourmaline.
SAPPHIRE 
Sapphiretranslated from Greek means “blue”. Surprisingly, this piercing blue stone is the closest relative of the blood red ruby. This is also corundum, and its color is due to titanium impurities. When growing artificial sapphires, titanium is also added, but it is extremely difficult to recreate the variety of color shades with which nature has colored the gem: this is soft blue, deep blue, indigo blue, lilac. There are also stones that have the effect of asterism. Such crystals are called star-shaped; under certain lighting, a sparkling six-ray star lights up in them. The hardness of the stone on the Mohs scale is 9 points.
Sapphire is one of the four most expensive stones in the world. It is more common than ruby, often in the form of very large stones. The most prized are the clear cornflower blue Kashmir sapphires, which are famous for retaining their color under artificial light, which is rare for this crystal. The juicier and brighter the blue of natural sapphire, the higher its price. Sapphire is very hard and can only be scratched by a diamond, making it perfect for rings and bracelets.
The name of this stone comes from the Greek "sappheiros" - a blue or blue valuable stone, although the Greek word itself possibly comes from the Babylonian "sipru" - scratching. Previously, only blue corundums were considered sapphire. Now these include corundums of various colors: yellow, purple, green, orange and colorless, except red. The color of the stone, as a rule, is specifically specified: green sapphire, yellow sapphire, etc. Otherwise, only blue or cyan sapphire is meant.
The powers that be have always had a weakness for the delicate shine of sapphire. Thanks to its marvelous heavenly coloring, it was already considered sacred in Ancient Greece and Ancient Rome and dedicated to the father of all gods - Zeus. Only priests can wear it in a ring on their index finger; the stone helps them hear and understand what the oracle says. Indian high priests wear a sapphire pendant on their chest, and this ornament is called Truth.
According to the book of the great Exodus, the god Yahweh gave Moses the Ten Commandments, engraved on sapphire tablets (large stones). In the Middle Ages, sapphire was revered as a symbol of holiness, infallibility and inviolability of power; kings abundantly decorated their crowns and other regalia with it. Boris Godunov, a great lover of gems, considered it the most beautiful and powerful talisman.
Amazingly beautiful sapphires are stored in the Diamond Fund of Russia. One of them, “Imperial Power” (200 carats), is mounted in the cross of the power of the Russian Empire, the other, cornflower blue, weighing 258 carats, is inserted into a precious brooch.
EMERALD 
Emerald- bright green beryl. Its green color is due to the presence of impurities of chromium, iron and vanadium. The hardness of the stone on the Mohs scale is 8. This is a very fragile gem, and often cracks and chips significantly reduce its quality. Therefore, the edges of the crystal are often covered with complex engravings to hide defects. Interestingly, this stone is almost always processed with a step cut, which is called emerald.
Emerald is a jewelry crystal of the highest class; many of them are more valuable than diamonds. The stone is especially valuable due to its density of color and transparency, the absence of inclusions and cracks.
Currently, artificial stones synthesized in Switzerland, France, and Germany are widely used in jewelry. Cut emeralds in jewelry, due to their uniform green color and strong shine, are not inferior to diamonds - both in cost and in their perfect beauty.
The green gem became famous as a talisman for mothers. They say he patronizes pregnant women. Egyptian priests ordered women expecting a child to wear a ring with an emerald and then place it in the cradle with the baby. People with poor memory and poor eyesight are advised to wear this mineral in necklaces and pendants around the neck, and it is better to wear a ring with it on the little finger.
Judging by the ancient Egyptian papyri, emerald has been known to man for at least 6.5 thousand years. From prehistoric times to this day, the gemstone has maintained a prominent position in the gem market, especially in the East, as it represents the sacred color of Islam. Emerald was Cleopatra's favorite stone. She presented close nobles with unique talismans with her image engraved on an emerald.
One of the most amazing legends about this stone is that the emerald fell from the head of Lucifer himself when he was expelled from paradise. The Holy Grail was carved from it, from which Christ himself drank at the Last Supper. On Golgotha, the blood of the crucified Jesus was collected in this cup, after which it acquired miraculous power - it bestowed many years of life on those who drank from it.
It is curious that the largest of the emeralds was found in 1970 in Ukraine. It was called “Jubilee Leninsky”. He weighs 5360 g (26800 carats), like an impressive watermelon!
ALEXANDRITE 
Alexandriteis a type of chrysoberyl, in Russia it is classified as a precious stone. It has a rare property - reverse, i.e. it changes color depending on the type of lighting: during the day its color range varies from dark blue to emerald green, and under artificial lighting alexandrite acquires a purple-red color.
Mohs hardness - 8.5.
The largest Russian alexandrite has a ton of everything 6 g . It is believed that the duality of the color of alexandrite is magically connected with the duality of human blood - arterial and venous, and the stone regulates hematopoiesis, purifies the blood and strengthens blood vessels. The ring with this stone should be removed before going to bed. Alexandrite makes its owner peaceful and accommodating.
If chrysoberyl matches its chemical formula exactly, it is pure and colorless, but this is exceptionally rare. Much more common are cloudy stones with a “cat’s eye” effect - cymophanes and varieties with a change in the color of the stone when the nature of the lighting changes (Alexandrite). Impurities of iron, chromium, and sometimes titanium cause the color of alexandrite to change from green tones in daylight to violet-red in electric light. In Russia, alexandrite is found as an associated mineral in the emerald mines of the Urals, where it was, in fact, first discovered.. Due to the rare occurrence and size of individual stones, there is no need to talk about its industrial mining in Russia. And in this regard, alexandrite is practically absent in domestic jewelry. Indeed, everything that is called alexandrite in the trade, upon closer examination, turns out to be synthetic corundum with the effect of changing color due to the addition of impurity elements. Alexandrite is found in much larger quantities in Brazil and Sri Lanka; the cost of large and clean stones can reach 20 thousand dollars.
AQUAMARINE
Aquamarineis a type of the mineral beryl. This stone shimmers in an unusually beautiful spectrum of light blue tones: from the light blue of the sky to the deep color of the sea. The color of the mineral can be compared to the color of sea water in tropical latitudes, and the color of the stone varies in different directions. When heated, aquamarine crystals can change their green outer color to a blue tint. A very wear-resistant, transparent and shiny stone, it always has high clarity, even if it is very large in size (although such stones are very rare). Dark blue aquamarine is always more expensive than light-colored stones. The light blue color of aquamarine awakens in us feelings of sympathy, trust, harmony and friendship. This color is divine, eternal, just like the color of the sky and the color of water, a color that gives the strength of life. It seems that the aquamarine has caught a piece of the ocean within itself. The main source of the most valuable dark blue stones is Brazil. Thanks to its mystical resemblance to sea water, aquamarine has long been considered a talisman for travelers. It is able to protect against seasickness and ensure safety on a sea voyage.
AMETHYST 
Amethystbelongs to the quartz group and is silicon dioxide. Hardness on the Mohs scale -7.
Color varies from almost colorless pale violet, bluish violet to purple, dark violet, almost black. Interesting samples with a color transition along the length of the crystal from violet to yellow - ametrine.
Under the influence of sunlight, amethyst gradually loses its purple color and becomes discolored. When heated to a temperature of 300 degrees Celsius, it completely loses its beautiful purple color. The nature of its color is very complex - it is caused by a combination of iron ions and defects in the crystal lattice.
Amethyst is the most valuable mineral in the group of quartz varieties.
The name amethyst comes from the Greek amethystos, which means inebriated. At that time it was believed that wearing an amethyst was not subject to intoxication. In addition, there was a belief that if you drink from an amethyst goblet, there is no danger of poisoning. One of the earliest mentions of amethyst is that it was one of the twelve stones that adorned the breastplate of the Jewish high priest who served in the Temple of Jerusalem. For centuries, ancient Greek and Roman magicians and sages believed that it could prevent intoxication.
TURQUOISE 
Turquoiseis an aqueous (hydrated) phosphate of copper and aluminum, but aluminum can be partially replaced by iron oxide. Turquoise, which does not contain iron, is colored blue in various shades - from sky blue to Prussian blue; the presence of iron usually gives the stone a greenish tint, which may intensify to the point where the mineral turns yellowish-green to apple green.
Regardless of the fashion for stones, turquoise has always been considered a talisman of health, happiness and good luck. Turquoise is an indicator of health.
Some stones fade and turn green when they change hands, thereby demonstrating amazing devotion to the previous owner.
Due to its relatively low hardness, turquoise is usually not cut and set into jewelry in the form of round stones of regular shape, called cabochons.
Turquoise (turquoise) owes its name to the French word Turkish (from pierre turquoise - Turkish stone). The Russian name comes from the Persian word “firuza”, which means “victorious, bringing happiness.”
Buddhists idolized turquoise because it was associated with the belief that it was thanks to it that Buddha was able to destroy the monster.
Turquoise was called the stone of victory and happiness. She was considered a military talisman. Turquoise was especially revered by the Aztec Indians of Central America: their leaders were buried with turquoise jewelry. Turquoise is the national stone of the Persian (Iranian) people; According to Persian beliefs, turquoise was formed from the bones of people who died of love. In Egypt, images of sacred scarab beetles were carved from turquoise. The name of the mineral itself comes from the Persian word “firuz” - “victorious”. The Armory Chamber of the Moscow Kremlin houses the throne of Tsar Boris Godunov with large inserts of first-class turquoise.
RHINESTONE 
Rhinestone- crystals of transparent colorless quartz.
The term “crystal” is a Russified form of the Greek word “kristallos” - ice; It is in this sense that it is used in the Iliad and the Odyssey. Later, but back in ancient times, due to its external similarity, transparent quartz, which was then considered strongly hardened ice, began to be called a crystal. Even in the 12th century. Marbod of Rennes wrote: “Pure crystal is ice that has hardened over many years...” In Russian terminology, until the second quarter of the 19th century. “crystal” and “crystal” were synonymous and were even used together. Only later did natural polyhedrons of minerals begin to be called crystals, and “crystal” with the definition “mountain” was assigned to quartz. Heavy, highly refractive glass is simply called “crystal”.
Balls were cut out of crystals for ritual and magical purposes, incendiary lenses, with the help of which priests lit fire on altars with “divine fire,” and “magnifying glasses.” According to ancient beliefs, rock crystal relieves bad dreams, in a ring it protects from the danger of freezing, etc. In the Armory Chamber of the Moscow Kremlin there are various vessels made of rock crystal: the samovar of Peter I, a barrel, a pepper shaker, a mug, bowls, “by hand,” etc. .d.
POMEGRANATE 
Pomegranate- a mineral of traditionally deep red color, a shade of “pure flame”, and high hardness. It is part of a group of silicates that vary greatly in color and contain various cations. In shape and color, the crystals resemble pomegranate seeds, hence its name. However, this gem is not only red.
There are six types of garnet: fiery pyrope, greenish demantoid, transparent lilac, purple or violet-red almandine, emerald green uvarovite, orange spessartine and grossular - the color of gooseberries.
Garnet is relatively inexpensive, and in beauty and depth of color it can easily compete with ruby and emerald. Fiery red pyrope was very popular in the last century, but the release of a large quantity of the mineral onto the world market unfairly relegated it to a minor gemstone.
Modern products widely use garnets processed in various ways - faceted, cabochon, polished; The ancient form of cutting is very common - in the form of a saucer, which increases the transparency of the gem.
Interestingly, jewelry with garnets was known back in the Scythian era. Europe first learned about this stone thanks to the crusaders, who brought it from the Middle East. The ancient Persians wore garnets as protection from natural disasters; they considered these stones to be royal, and the profile of the ruler was often carved on the surface.
PEARL 
Pearl- round or irregularly shaped shiny formations with a mother-of-pearl tint, which arise when layers of aragonite (calcium carbonate) are deposited around some foreign center, most often grains of sand, in the cavity of marine and freshwater mollusks that have a shell with a mother-of-pearl inner layer.
It is characterized by soft, delicate, faintly noticeable tints of color, a smooth matte surface and a bright spot of light on it, a natural spherical shape.
Color: white, pale pink, pale blue, pale green. It also comes in yellow, red, blue and even black. The ideal shape of a pearl is round. But there are also elongated, pear-shaped, irregularly shaped specimens.
diseases.
Nature gave pearls a short lifespan, lasting more than two or three human generations. To prevent pearls from aging, they must be worn, but should not be kept in bright sun for a long time.
Harvesting pearls from the bottom of the sea is a difficult and dangerous business. Among the 40-50 shells caught, only one contains a treasure. The price of a pearl increases tens of times for every millimeter in diameter, but its value is determined not only by its size, but also by its brilliance, color, and shape.
The world's most expensive pearl, La Regente, of perfect proportions and weighing 15.13g, the size of a golf ball, was sold at auction for $864,300. The largest is the “Pearl of Allah”, in shape and size resembling a head in a turban, weighing 6.5 kg, found in 1934. near the Philippines.
At the end of the 19th century, a young entrepreneur, Takiche Mikemoto, unraveled the secret of the birth of mother-of-pearl peas. He introduced a grain of sand into the shell and after a couple of years he received cultured pearls. With this he delighted women all over the world. More than 200 tons of cultured pearls are produced in Japan every year. Only special devices and unique craftsmen can distinguish it from natural ones.
Pearl jewelry has been known almost since prehistoric times—for 6,000 years.
TOPAZ 
Topaz- a very hard (cuts glass) mineral aluminum fluorosilicate.
The color of the stones is determined by the admixtures of titanium, iron and chromium. The color range of topazes is very rich. They can be colorless, pink, yellow, golden, blue, red-orange, purple, wine, brown. There are yellow stones with a “cat’s eye” effect. Polychrome minerals look very beautiful, in which one part can be blue and the other cherry. It has one more characteristic feature - faceted crystals are very slippery to the touch and easily slip out of your hands.
The word “topaz” comes from the Sanskrit tapas - “fire”, “flame”, “heat”.
Colored varieties of the mineral gradually fade from bright light, so it is better to store it in the dark.
Topaz has every reason to become a favorite - low price, high hardness and, of course, outstanding appearance. The most valued are: violet, as well as yellow, peach, orange and purple - they account for less than 0.1% of the total topaz market! The most popular are blue and blue varieties. Half a century ago, a method of refining was discovered that gives such shades greater brightness and depth. It is amazing that many colorless stones acquire a dazzling shine after cutting - they can easily be confused with a diamond!
STRUCTURE AND PROPERTIES OF DIAMONDDiamond structure
Diamond- This the hardest mineral not only on Earth, but also in the Universe (10 units on the ten-point Mohs scale). It consists of carbon, which is the closest packing of carbon atoms. an unusually hard, but at the same time fragile stone, which, with a sharp and strong blow, can break into pieces.
Graphite structure
Diamond crystals are completely transparent (if there are no cracks in them); they can be not only colorless, but also yellow, blue, green, pink, brown, and gray. Natural diamonds are rarely black in color. Diamonds are found not only in the form of single crystals, but also in the form of intergrowths, spherical aggregates, and fine-grained aggregates of irregular shape.
Appraisers count 1,000 natural jewelry varieties of diamonds.
They take into account color, transparency, fracturing, crystal shape, presence of inclusions and other parameters of the raw material. The subtlest changes in shades of stone color and transparency, the direction of cracks, accumulations of inclusions and other subtle nuances are taken into account.
Brightly colored diamonds have always been highly prized by both master jewelers and stone buyers. Large stones were always described in detail, they received their own names. Their history has been carefully recorded.
A cut diamond is called diamond. There is a special diamond cut, although each stone is cut individually, and the master cutter looks at the shape and color of the stone to determine which cut to choose.
HOW ARE DIAMONDS FORMED?
How, under what natural conditions, could carbon, which on the surface of the Earth is represented by one of the softest minerals - graphite, be grouped into the densest structure of diamond?
There are several theories, but the most reliable is the theory according to which diamonds formed in the Earth’s mantle, at a depth of about two hundred kilometers, and at a pressure of at least 50,000 atmospheres. At the same time, in the depths of the young, forming Earth, excess pressure was created, gases and solid matter exploded onto the earth's surface. In bedrock, kimberlites, diamonds are found in the so-called explosion tubes. These are unique structures with a diameter of a kilometer or more, oval and round in shape. They are filled with bluish brecciated kimberlite(belongs to ultramafic rocks) and go to a depth of perhaps tens, and maybe hundreds of kilometers. Diamonds are found among kimberlites. The age of such diamonds is very long - it ranges from one hundred million years to 2.5 billion years.
If a kimberlite pipe reaches the Earth's surface, it is destroyed by rock weathering processes. Diamonds move along with the rock and end up on mountain slopes in loose rocks and in rivers, among sand and pebbles. Such deposits are called in scatterings. Diamonds are mined from them in the same way as gold - by washing rocks, manually or using simple equipment.
If large meteorites fall to Earth, then their speed, in the atmosphere and upon impact, is very high (we all remember with what unimaginable speed the Chelyabinsk meteorite flew by). When hitting rocks consisting of carbon (coals, carbonaceous shales), diamonds can also form. For example, in the north of Siberia (the border of the Krasnoyarsk Territory and Yakutia) there is a structure (large crater) formed by a meteorite impact - Popigai astrobleme. The diameter of the crater is about one hundred kilometers, the event occurred 36 million years ago (geological period Eocene). Within the crater there is a large deposit of diamonds formed as a result of the impact of a meteorite on carbon-containing rocks (impact diamonds).
Diamond deposits are not rare; they have been found on all continents of the earth, with the exception of Antarctica. In Russia, the most famous deposits are in Yakutia (Peace Pipe) and the Arkhangelsk region. Industrial diamond mining is carried out in the Republic of South Africa, Botswana, Canada and Angola.
FAMOUS DIAMONDS
Here I would like to mention only the most famous diamonds, the names of which have been included in films, books, are often mentioned and are widely heard. In general, there are several hundred large diamonds found both in our time and over the last two millennia. Among them are many stones covered in myths and legends, with their own, often bloody and ugly stories associated with robberies, murders and palace coups.
Cullinan- a transparent, colorless diamond, was found in 1905 in the Republic of South Africa. It had dimensions of 50x65x110 millimeters. This stone was used to create 105 cut diamonds, including a diamond called the Star of Africa, which was then set into the scepter of Great Britain (British Empire).
Diamond Cullinan
Kohinoor- a transparent, colorless diamond found in India around the year 800 AD. Diamond has a rich history; it has changed its owners many times and passed from hand to hand. Now this famous diamond is in Great Britain, it has been cut and inserted into the crown of Queen Elizabeth.
Diamond Kohinoor wearing Queen Elizabeth's crown
Almaz Orlov- a stone stored in the Diamond Fund of Russia. This diamond also has a rich history, having been found in the 17th century in India. Currently inserted into the imperial scepter of Catherine II.
Diamond Orlov in a scepter
Great Mogul- This large diamond was found in India in the 17th century and also has a long and rich history. A diamond weighing 279 carats was cut from it.
Diamond the Great Mogul
ASTROLOGY ABOUT DIAMONDS
This stone is considered a symbol of fortitude, strength of intention, physical strength and spiritual fortitude, purity, infallibility and indestructibility. Diamond jewelry can be worn by representatives of all zodiac signs, but they are especially good for Aries, Virgo And Libra.
18.12.2018
More than once we have heard the statement: strong as granite. And this is well deserved. Granite, syenite, labradorite, black gabbro- These are the strongest and hardest rocks. They were formed millions of years ago directly from magma, as a result of its gradual cooling in the depths of the Earth, under very high pressure, liquid rocks crystallized and formed a very dense rock (density from 2400 to 3000 kg/cub.m), the structure of which is granular, full-crystalline, and the texture – noticeable, even massive. Their compressive strength is also impressive - up to 300 MPa (for comparison, the hardest brick has a maximum of 150 MPa). And other characteristics are amazing: being completely immersed in water, gabbro rock withstands up to 100 cycles, and granites - up to 200 cycles of alternating freezing/thawing (the same brick - maximum 15). The wear of these rocks is less than 0.12 mm per year, provided that a million people walk on the stone this year.
Such a different stone
All of the listed deep rocks are quite similar in appearance. It is often very difficult for a non-professional to distinguish gabbro diabase from fine-grained granite. Likewise, labradorite, which has a black color and dark blue veins, is very similar to black granite, although the latter is more uniform. The reason for this similarity is that all these rocks have almost the same mineral composition, which includes spar, quartz, mica, and non-ferrous minerals, but the proportions of their content differ.
Granite has the most different types, colors and textures. For example, in Russia there are deposits of red-brown, white and gray varieties, very valuable black Karelian granite. In Ukraine and Belarus, there are mainly gray and red shades. Spanish granites are greenish, pink and black, while Italian ones are all shades of gray. China is richest in multi-colored granites: pink, yellow, green of all shades and blue-black. The finer the grain size, the stone is harder, more durable and frost-resistant. Weathering resistance and acid resistance are greater in those varieties that contain more silicon dioxide. And beauty depends on the amount of mica that sparkles and shimmers in the sun. True, at the same time its presence worsens the construction quality.
It is impossible not to mention some of the limitations associated with the use of this type of natural stones. Firstly, granite gabbro diabase quite heavy material. That is why only the cladding of buildings is made from it - façade and interior. And, also used for paving, made monuments from
granite and gabbro, used in landscape design for the construction of alpine slides and rockeries. The second point that must be taken into account is that granites are quite fragile, therefore, in order for the cladding made of them to withstand shock loads, they must have a certain thickness, and also, a special installation method is used. Third, hard rocks crack at temperatures above 650 degrees Celsius. Therefore, they are not used to lay out the fireboxes of even very solid fireplaces, but only for their cladding.
Volcanic rocks
In addition to materials such as black granite
and gabbro, hard rocks also include basalts, liparites, diabases, porphyries and trachytes. In their composition, they do not differ from deep-seated stones, but were formed under slightly different conditions - as a product of volcanic activity. Trachytes and porphyries have a very beautiful texture and color, their density and processing capabilities resemble marble (2600-2800 kg/cub.m.) and are used as a finishing material. Basalts and diabases are denser - up to 3200 kg/cub.m, have a more modest color - black, gray in various shades with green and are more often used for finishing foundations, constructing retaining walls, and paving. Gabbro paving slabs have virtually no wear. For example, the coverage on Red Square, despite the fact that several million people pass there every year, shrinks during this time by less than half a millimeter.
What in inanimate nature fascinates and amazes people more than gems? Precious stones are amazingly beautiful and rare, possessing them makes a person wiser and more majestic - in any case, this is what numerous legends and beliefs associated with these most beautiful of minerals claim. But which stone is the most expensive in the world? Let's find out the opinion of experts about the cost of the most expensive stones.
10 Emerald and sapphire
On average, a good sapphire (about 6,000 per carat) turns out to be more expensive than a not very high-quality emerald. This certainly applies to regular blue or light blue sapphire. As for the rarest orange gem (it is called padparadscha), we will talk about it further. This is certainly 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 who are valued so highly.
There are a couple of amazing examples to note. Firstly, this is the Millennium - a 61 thousand carat sapphire, decorated with carvings - 134 portraits of the world's most prominent celebrities of the millennium, including, for example, Beethoven, Shakespeare and Einstein. Its current price is $180 million.
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 USA. 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 explained not only by its beauty, but also by the exceptional rarity of the gem.
The precious stone 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 looks set to leave all others behind - it is 58% harder than diamond.
Zicheng Pan from Shanghai Jiao Tong University and his colleagues modeled how atoms in two substances supposedly having the properties of very hard materials would react to the influence of a special sensor.
Extreme conditions
The first is wurtzite boron nitride, which has a structure similar to diamond, but consists of different atoms.
The second is the mineral lonsdaleite, or hexagonal diamond, made up of carbon atoms like diamond, but they are organized differently.
Modeling showed that wurtzite boron nitride can withstand 18% more impact than diamond, and lonsdaleite - 58% more. If the results are confirmed by 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, while wurtzite boron nitride is formed during volcanic eruptions under high temperatures and pressure.
Flexibility
If successful, wurtzite boron nitride may become the more useful of the two due to its resistance 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 the surfaces of spacecraft, 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 bonds change direction by 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, Las Vegas.
Scientists emphasize that in order to prove the theory, single crystals of each material are needed. There is currently no way to isolate or grow such crystals.
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