Oxides and hydroxides: Quartz

Diagnostic card.
On the picture. A beautiful group of quartz crystals from Arkansas. Quartz often forms aggregates of crystals of large size, usually growing one on the other on the parent rock (druses).

SiO2
The trigonial trigonometric system
Hardness 7
Specific weight 2.65
Cleavage is absent
Cracked shell
Color is colorless, differently colored
Color in powder white
Glitter glass

This is the most common mineral present in almost all rocks. It is rich in varieties, very common and highly valued. Quartz is a rock-forming mineral and at the same time belongs to the number of ornamental and precious stones. Due to its properties, it is very resistant to both mechanical and chemical influences, and therefore is the most abundant mineral on Earth, in the upper part of its crust. As a main rock-forming mineral, as a rule, only a cloudy, milky, or veiny quartz occurs. Painted varieties of quartz, as well as its colorless transparent crystals (rock crystal) - are popular jewelry and ornamental stones.

Chemically, quartz is very stable, only dissolved in hydrofluoric acid. Large crystals (trigonal) are usually columnar, have the form of a hexagonal prism with rhombohedral end faces. Quartz is an important raw material for the glass and ceramic industries. In technology, it is used to generate ultrasound, as well as in radio transmitters and clocks (due to the inverse piezoelectric effect of its crystals).

Rock crystal is a crystal of typical shape. The cross-hatching, noticeable on the faces of the prism, serves as an important diagnostic feature of all varieties of quartz. Physical properties are typical of quartz.

There are two groups of quartz. One includes well-formed crystals, distinguished by the naked eye, the other is aggregates of microscopic crystals. The first group includes, on the one hand, impurities, colorless and transparent quartz (rock crystal), on the other - varieties, painted in different colors, due to impurities. They are: amethyst (violet), smoky quartz (rauchkvarts, obsolete rouxtopaz), or morion (black), citrine (yellow), blue quartz (iris), rainbow quartz, rose quartz, green quartz. Impurities can look like shiny scales (aventurine), needles of rutile (rutile quartz, or hair of Venus) or other fibrous minerals ("moss").

A typical form of a single crystal of quartz is a prism of hexagonal section, terminated by pyramids. In many instances, it is seen that the three faces of the pyramid alternate with the other three, but smaller. In the photo: quartz crystal with inclusions of tourmaline.

The second group of species includes chalcedony, jasper, flint. Chalcedony, in turn, includes varieties well familiar to everyone: carnelian-carnelian, agate, onyx.

Diagnostic signs.
Quartz is very hard, it can not be scratched with a knife (or other sharp iron object). When sawing or when striking with a hammer, it glows yellow, as seen in the dark (triboluminescence).

Origin.
It is believed that about 12% of the earth's crust is quartz. It crystallizes together with the magma or is formed under the action of fluids at a temperature of 100-400 degrees. C. Since quartz is very stable and difficult to weather under the influence of atmospheric factors, it is the main component of sands and other sedimentary rocks. Quartz is also common in metamorphic rocks.

Application.
Quartz finds the most diverse application: from high technologies (oscillators, frequency stabilizers, ultrasound generators) to the production of glass, cleaning products and jewelry.

Place of Birth.
Large crystals of diverse shapes are found in Madagascar and in Brazil. Huge specimens, the weight of which is measured in tons (up to 40 tons), found in different places in Brazil. An unusual collection of giant crystals exhibited at the National Museum of Natural History in Paris. Quartz often forms veins in rocks. Sometimes they contain rounded voids (geodes), the walls of which are entirely covered with quartz crystals.

Quartz. Drusa crystals, painted with goethite. Wolf Island, Onega Lake, Karelia, Russia, CIS. Photo: © А.А. Evseev.

Quartz: Smoky quartz

Prismatic crystals of smoky quartz in a metamorphic rock. Crystals are a typical quartz shape: prisms, crowned with pyramids.

This is a very common type of quartz, different in color and shape. Smoky quartz is found in the form of smoky brown crystals of prismatic appearance. They often form groups of many individuals, as well as twins. Their sizes range from microcrystals to gigantic ones of several meters. The color of smoky quartz is associated with the action of radioactive substances on the initially unstained crystals.

Most of the crystals lose their color when heated to 300-400 ^° C, the rest become yellow. In smoky quartz, fracturing, fluid inclusions, needle crystals of rutile, red garnet crystals, and void geometric outlines (negative crystals) can be observed.

Deposits and applications.
The most significant deposits are found in Brazil, Madagascar and Sri Lanka. Giant crystals were mined in Tizengletcher (Switzerland, canton Uri). Due to their beauty, the best specimens are meant for jewelry use.

Use in jewelry.
When using smoky quartz in the jewelry business, facet cut, facet cutting or steps are common; You can also use an oval or, more rarely, rotunda. If there are interesting inclusions of rutile in the stone, a sphere or cabochon is preferable.

Quartz: Amethyst

This many glorious variety of quartz is distinguished by a rather intense violet color. In many crystals of amethyst there is a strongly developed prism, crowned with colorless pyramids. The color of amethyst is due to the phenomenon of radiation of a natural crystal containing iron. As a rule, it is distributed unevenly: either by zones parallel to the main facets of the crystal, or concentrates only on the ends of the crystal.

Glass shine is often attenuated on the faces. Inside the crystal, various inclusions can be observed: liquids in flattened voids of zigzag shape, brown needle or pink crystals collected in bundles.

All amethysts when heated to 400-500 deg.C are converted to quartz-citrine.

Deposits and applications.
Amethyst is found mainly in geodians in basalt rocks. It is this amethyst that is observed in the fields of Brazil, Uruguay and India. Brazilian geodes, having a rounded shape, are measured along the outer contours by cubic meters. In Russia and in Madagascar, the amethyst fills veins and voids in pegmatites. Amethysts (including artificial crystals) are used mainly in jewelry.

Use in jewelry. Amethyst since ancient times was the most common stone in the jewelry business. Varieties of both pale and intensely colored faceted in the form of cabochon or tono or facets, as well as in the form of a diamond. In the old days a lot of cups and other objects of applied art were made of translucent amethyst aggregates.

Quartz: Citrine

The color of this yellow and golden variety of quartz is determined by the presence of oxides and hydroxides of iron. The color varies from pale and intense yellow to orange-yellow and brownish.

Deposits and applications.
It occurs in pegmatite rocks enriched in silica, often together with tourmaline, beryl and micas. The best in terms of purity and size are found in Brazil, in the Campo Bellu and Seto Lago-As areas (Minas Gerais). In other places in Brazil, known for quartz-citrine finds, the samples are less clean and of high quality. In the Urals (Murzinka) and Madagascar, no less valuable crystals were found.

Other deposits (in which, however, crystals of jewelry quality were not found, and this is the main sphere of use for citrine) - Pikes Peak (Colorado, USA), Burg-d'Ousan (Dolphinato, France), Inijoso de Duero , Villa Buenas and Villa-Beso (all near the city of Salamanca, Spain).

Use in jewelry.
Citrine is often used for cutting - for this, crystals should have optimal transparency and uniform coloring; If they have inclusions, they should not be visible to the naked eye. In addition to being used as a precious stone, citrine finds application as an ideal stone for decorative and applied purposes and sculpture.

Quartz: Aventurine quartz

This species is not found in the form of well-formed crystals. Massive formations with a lot of chaotically distributed crystalline inclusions are characteristic.

If light is reflected from the surface in the form of many brilliant points, one speaks of the phenomenon of "adventurism" as a flicker caused by inclusions. In the adventurine of milky-green color (the most common and used variety) inclusions are represented by scales of fuchsite - green chrome mica. In other cases, both the background color and the reflections are associated with brown, white and silver mica, red hematite and blue dumortierite.

Green quartz aventurine contains inclusions of leaves of chrome-containing mica - fuchsite, golden-brown - hematite (or muscovite). The most significant deposits of aventurine are in India, Brazil, the CIS. It is used as a material for the manufacture of artistic products and cabochons. We especially like this stone in the countries of South-East Asia. It can be confused only with aventurine feldspar, and the green variety with greed.

Deposits and applications.
Aventurine is not too common. Its main deposits are in India and Egypt (developed mainly in the past), Russia, Brazil, Chile and Spain. He was met in Val de Sousa (province of Turin). Aventurine is used exclusively in jewelry.

Use in jewelry.
Aventurine basically gets a cut in the form of a sphere for a necklace, as well as earrings; In the form of a cabochon oval shape - for brooches and pendants. Very rarely it is processed in the form of a hoop for bracelets. In the past, vases and bottles were made from it, now - only small sculptures. Today aventurine quartz is extremely rare, it is very difficult to meet in the form of products and inserts in jewelry.

Quartz: Prasem and Praseolite (Green Quartz)

Occasionally there are crystals of a green variety of quartz (prazem). More common microcrystalline mass, whose green color is due to the inclusion of green amphiboles and chlorite. A dense quartz unit. The onion-green color, which defines the name of the stone, is due to inclusions of actinolite fibers. In Europe it is found in Germany (Ore Mountains), in Finland. Austria (the Salzburg Alps). Scotland. Sometimes, green jasper is also called prazem.

The most popular samples from collectors from the island of Elba and from Mar-Egeo. Use in jewelry is quite limited. If the stone has a particularly intense green color, it is processed in the form of a sphere or cabochon. It is also used for making intaglios and small art products. It is easy to confuse with greed.

Today prazem often goes on sale under the name of jade or jadeite, although there is nothing to do with jade and jade quartz with green inclusions. Prasem also can be called green aventurine or aventurine quartz. Crystals of prazem are extremely rare and expensive.

The onion-green coloring determined the name of praseolite - this transparent green variety of quartz: in Greek prasios - green as leeks. In nature, an ideal-transparent green quartz of this color is not found - since 1950 it is obtained by calcination at 500 ^o C of amethyst and yellowish varieties of quartz from the Brazilian deposit of Moktesuma (Minas Gerais). Recently, the cutting material comes also from Arizona (USA). It looks like beryl, peridot, tourmaline.

Quartz with inclusions, andradite. Synerechenskoye deposit, Primorye, Russia. Photo: © А.А. Evseev.

Quartz with inclusions of chlorites. Himalayas, Nepal. Photo: © А.А. Evseev.

Quartz: Blue or blue (sapphire) quartz

Contains inclusions of various minerals - sodalite, dumortierite, rutile, magnetite, etc. Blue quartz is used in jewelry as an ornamental stone for cutting into cabochons, for making sculptures and mosaics.

It comes mainly from the deposits of Brazil (Bokeyra, Bahia). Other notable deposits are in the USA. In Italy, there is a blue quartz, the color of which is due to an admixture of magnetite.

In jewelry to meet natural and natural blue or blue quartz is almost impossible. Forming blue crystals quartz is extremely rare and very expensive. There is a synthetic blue quartz.

Coarse aggregate of quartz. Inclusions of crocidolite fibers determine the grayish-blue color of the stone. Deposits are known in Austria (Salzburg), Scandinavia, South Africa, Brazil. It is used as an ornamental material.

Quartz: Quartz with inclusions

About fifty kinds of minerals are known, which can be found in quartz as inclusions. They are sometimes oriented in separate geometric directions, which creates a pleasant aesthetic impression. Especially popular are varieties with needle inclusions of hornblende, tourmaline, chlorite and rutile. In the latter case, the mineral is called "Venus's hair," especially if the needles are golden, straight and pointed.

Quartz: Rainbow quartz .

This is the name for transparent quartz, which, due to numerous microcracks, has a rainbow effect. It is formed under long-term stress conditions during crystallization in the pneumatolitic phase. The best specimens were delivered from several fields in Brazil (Minas Gerais state). This kind of jewelry is highly valued. The cut is usually done in the form of a cabochon or sphere, since the rainbow effect is best seen on a curved surface. In the Alps, rainbow quartz was found in Saint Gothard (Switzerland) and Val Malenko (Sondrio province).

Quartz: Pink quartz .

Its name was received in color; Often is turbid and fractured. Crystals with distinct facets were only recently met. The color in the light fades. Sometimes an asterism occurs: the thinnest nodules of rutile, oriented along the crystallographic axes, determine the appearance of a six-pointed star. The main supplier of rose quartz is Brazil, the most high-quality material comes from Madagascar. It is processed in the form of cabochons, beads, serves as a raw material for artistic products. Only very rare large transparent areas are to be cut.

Quartz: quartz aggregates .

A quartz cat's eye . In the drain quartz sub-parallel thin fibers of light fibrous minerals (for example, actinolite) are located; On the surface of the cabochon at the turn runs a narrow moving light strip: then the stone really resembles the cat's eye, hence its name. Speaking about this stone, it is necessary to use the definition of "quartz", since just a cat's eye is a mineral of cymophanes. It is sensitive to acids. Deposits are well known in Sri Lanka, also found in India, Brazil. The stone is not difficult to be confused with cymophane (chrysoberyl).

Falcon eye . This is a siliceous aggregate of a bluish-gray amphibole - crocidolite with a fibrous texture: on the polished surface of the light ebb; In the fracture silky shine. The stone is sensitive to acids. It occurs in the same deposits as the tiger's eye. Used in small plastic, for making beads, inserts for rings and earrings. Rounded cabochons with a narrow light strip on a bluish-blue background evoke in the memory eyes of birds of prey, where the name came from. The remaining properties are indicated in the description of the tiger's eye.

Tiger's eye . In its structure, the tiger's eye is analogous to the falcon's eye, in which the amphibole (crocidolite) is replaced by iron hydroxides, which give the stone a golden brown color. Wave-shaped ebb is created by a fine-grained structure. The gloss in the fracture is silky. It is unstable to acids. It occurs together with the falcon's eye in the form of plastoid bodies with a thickness of several centimeters. The amphibole fibers are oriented perpendicular to the surface, they developed along cracks, were subsequently replaced by iron hydroxides, and then silicified. The most significant field is in South Africa, in addition, there are deposits in Western Australia, Burma, India, USA (California), Ukraine. Light reflexes are the same as those of a cat's falcon eye.

Quartz: General information .

Although quartz is one of the most common minerals and its crystalline forms are easily identifiable, it should in no way be excluded from the category of precious stones. There are no other minerals that would have such an amazing violet color (amethyst). Yellow quartz can compete in beauty with topaz. Their similarity is so great that they have been confused for a long time, and only in recent years the international nomenclature composed by authoritative persons has forbidden using the term "topaz" to refer to yellow quartz. The usual colorless quartz, known as rock crystal, can be so brilliant and water-transparent that its sparkling stones are sometimes called diamonds, despite the almost complete absence of a play of light in them. Such a confusion of names, however, can mislead only a completely ignorant person. Quartz excellently serves in all those cases where purple, yellow or smoky stones are required: it is sufficiently stiff and firm to be worn, and has the dignity that its price is moderate. Despite the absence of the game, it can replace pastas in some jewelry because it is more sturdy. Quartz sometimes contains internal fibers and forms a very beautiful "cat's eye," which, although it does not have such a vivid opalescence as a chrysoberyl cat's eye, still can compete with it. Quartz also forms a kind of variety, known as the "tiger's eye".

Chemically pure quartz is devoid of color, it is water-transparent. It was about this species, when it was first discovered in the Alps, thought that it was a form of frozen water, and therefore called it crystal (from the Greek crystal - ice). This species is still known as "rock crystal". It has already been mentioned above that such sparkling stones in faceted form were sometimes called diamonds. So, in England used the terms "cornwell diamond" or "bristol diamond"; There are many more such names, for example, "Alaskan diamond", "Arkansas diamond", "Bohemian diamond". Such misleading names are not currently used by respectable jewelers, since, according to the "Trade Records Act," they are incorrect. For the first time the name "quartz" (quartz) was applied, apparently, by miners from the Ore Mountains. In the old days, the identity of the material, later called crystal, and the shapeless masses of silica carrying the veins, was not realized, and it can be assumed that the latter were first called Querkluftertz, which was reduced to Querertz and finally to Quartz, or Quarz, in modern German.

"Citrine" is the correct name for the yellow variety of quartz. It comes from the French word citron (lemon) and is given to this stone because the color it resembles some kinds of these fruits. However, until the nature of the minerals was deciphered, the yellow quartz was confused with the yellow topaz. Although this topaz has long been identified as a special mineral species, many jewelers stubbornly called yellow quartz "topaz", and this topaz was distinguished by the addition of the definition "Brazilian". Confusion, therefore, only worsened, since both yellow quartz and yellow topaz are abundantly found in Brazil. For the designation of yellow quartz, the names "Western," "Spanish," and "false topaz" were also proposed, but the use of the term "topaz" to refer to quartz is now recognized as an illegal trade description.

Kerngorm (original and more correct name - "Kerngorm stone") - brownish or smoky yellow quartz. It is named so because many samples of this variety of quartz were found earlier in the Kernhorm mountains in Scotland. The English word cairngorm is a slightly modified form of the Gallic word carngorm (blue core). He was wrongly called the Scottish topaz. Stones with a more dense brownish-smoky coloration are known as "smoky quartz". "Morion" is the name given to the smoky brown or black quartz.

Pink quartz, which, as the name indicates, has a pink-red or pink color, fades in strong sunlight. This kind of quartz rarely forms cut crystals and at best only partially shines, and is also more or less excised by cracks.

Milk quartz is almost opaque and resembles the color of milk. Rainbow quartz, or iris, is a quartz containing cracks. It got its name because of the color effect that occurs when light interferes with these cracks. Cracks can be obtained artificially by heating the stone and then quickly cooling it by immersion in water. In such cases, the effect can be enhanced by introducing a colorant into the cracks.

The color of quartz presents an interesting and as yet not completely solved problem. The color of the minerals can be caused by the presence of impurity elements entering the structure or the sites of the atoms of the main elements, or in the intervals between them. So, the color of amethyst was explained by the presence of manganese, and the color of pink quartz - by the presence of manganese or titanium. However, the spectrographic study did not confirm this assumption. In one of a series of studies of amethyst, sharp lines of aluminum, chromium and copper and weaker lines of magnesium and titanium were found. Measurements carried out on a series of samples of smoky quartz and amethyst from a number of Japanese deposits showed that the color density is proportional to the iron content. In twinned and zoned crystals of amethyst, the content of iron in different zones is different. It is now assumed that the color is associated with the presence of iron, but it should be expected that the simple presence of its atoms in the structure as an impurity will give shades of green or yellow. There is another way to create color, namely the emergence of color centers as structural defects that are formed under the influence of radioactive radiation. In natural colored crystals, the color is presumably due to the effect of small doses of radioactive radiation emanating from the enclosing rocks. It has long been known that the color of quartz is unstable to high temperatures, and its disappearance can be attributed to the destruction of color centers as the primary structure is restored.

Thermal action usually causes a weakening of color; If it proceeds long enough, and the temperature is high enough, it leads to complete disappearance of the color. Thus, the chernigram or citrine lose color with mild heating, amethyst - stronger, and pink quartz - with red heat. With weaker heating, the amethyst changes color to a dense orange color. Quartz, which has acquired a yellow color upon heating, differs from natural yellow citrine by the absence of dichroism; Citrine is invariably characterized, albeit with a weak but distinct dichroism. After accidentally discovering that some Brazilian amethysts, under the influence of heat, can turn into transparent green stones, the heating process was deliberately carried out and received material sold in New York under the name "praziolite" (an unfortunate choice, since the term "praziolite" was used in mineralogy To denote the products of a change in cordierite). The irradiation returns the color to the discolored quartz; While the new color will not necessarily be the same as the lost one. In most cases, such a quartz becomes smoky or black, although a small fraction of the crystals acquire the color of citrine. When the stones are repeatedly heated, a rapidly disappearing blue color is observed. There is no real amethyst color, although there are reports of the synthesis of amethysts with the growth of quartz crystals in steel autoclaves.

Prasem, or the "mother of the emerald," as it was sometimes called, believing that it is the mother rock for emeralds, is quartz, colored in an onion-green color due to the inclusion of actinolite (calcium-magnesia silicate) fibers. The word "prase" (English prase) comes from the Greek word "bow". This name is also attached to similarly colored microcrystalline aggregates of quartz (chalcedony).

Quartz (along with corundum) with respect to the simplicity of the chemical composition is located in a row of precious stones after the diamond being just a silicon oxide, or SiO2 silica. At high temperatures, silica forms other structural modifications.

X-ray diffraction study of quartz crystals confirmed the conclusion made on the basis of morphological and optical features, namely, that the structure of quartz has a spiral, that is, helical character; In accordance with this, two types of structure are distinguished: right-sided and left-sided. Indeed, amethyst is invariably represented by separate crystalline twin individuals, which are alternately right-handed and left-handed crystals. In some crystals, in a section perpendicular to the edge of the prism, one can see triangular sectors, which are represented by alternating right-handed and left-sided quartz and have different colors - violet and white.

In accordance with the type of symmetry, quartz is an optically uniaxial mineral and has two main refractive indices - ordinary and extraordinary. The first - 1,544, and the second - 1,553; The maximum birefringence is 0.009. The fact that deviations from these values ​​are very rare, proves the chemical purity of the transparent material. For some colored stones, there was a slight increase in the refractive index values ​​to 1.545 and 1.554, respectively.

The density of quartz is surprisingly constant, although it is more variable than the value of the refractive index, because of the presence of voids and inclusions. Density of rock crystal 2,651; The density of citrine, amethyst and rose quartz varies from 2.647 to 2.656, and the density of aventurine reaches 2.66-2.68. The hardness of quartz on the Mohs scale is 7. Quartz is not scratched by a steel knife and is resistant to abrasive action of ordinary dust. It does not have a cleavage.

With the exception of fibrous differences processed in the form of a cabochon to reveal the effect of a "cat's eye", quartz is usually subjected to a stepped or diamond cut according to the purpose of the stone. In addition to the fact that quartz produces jewelry material, it is a very valuable mineral. Owing to their high hardness, quartz is sometimes preferred to glass as a material for the manufacture of eyeglass lenses, since such lenses are not easily scratched during normal wearing and their surface retains polishing for a very long time. Quartz is superior to glass for transparency for ultraviolet rays, which is usually the most sensitive film, so it is used to make lenses used in thin photographic works. Balls of colorless transparent quartz are valued by admirers and lovers of beautiful stones.

Due to its piezoelectric properties, quartz was unexpectedly an invaluable material for manufacturing frequency stabilizers for radio waves. In quartz plates, rods or rings, vibration can be caused by electric excitation, and the stability of mechanical oscillations can ensure the stability of electrical oscillations. In this case, the fact is used that the amplitude of the latter increases unusually when their frequency coincides with the frequency of the former. The same principle is used when creating high-precision clocks. Obviously, quartz crystals used for such purposes should not contain traces of twinning, because otherwise the piezoelectric axes would be distorted and the ability to oscillate is broken. 'Experience has shown that many quartz crystals that seemed monocrystalline are in fact twins and therefore are not suitable as oscillation regulators.

Quartz sand is widely used as an abrasive for the manufacture of "skins" and cleaning pastes, and as a component of glass batch. When melting in an oxygen-hydrogen flame, quartz turns into quartz glass, which has completely different physical properties compared to conventional glass. Quartz glass does not have birefringence, and the refractive index is reduced to 1.460. The variance is 0.008. The density decreases to 2.2, and the hardness decreases to 5 on the Mohs scale. Quartz glass is widely used in laboratories and in households, because it can withstand rapid and uneven heating without risk of cracking. It can be stretched into a fiber that is as thin as silk, but does not have a tendency for torsion characteristic for the silk, and therefore such a fiber is invaluable in thin torsion experimental devices, for example, in instruments used to determine the mass of the Earth.

Quartz is one of those gems that are most easily identifiable by both optical properties and density. A colored boundary visible under white illumination on an ordinary refractometer is very characteristic and sharply differs from the pattern observed in the case of a glass with the same refractive power. The density of quartz also differs from the density of other precious stones, with which it can be confused.

The color of amethyst is so peculiar that it is not necessary to conduct any research to determine this stone. The easiest way to confuse other precious stones of the same color is yellow quartz and citrine. It has already been mentioned that it is easy to take them for topaz. Immersion in methylene iodide allows them to be recognized immediately, since the topaz is drowning in it, and quartz easily floats up. Since acid igneous rocks are defined as rocks containing an excess of silica, such rocks usually contain a lot of quartz. It is also the main component of sandstones, formed due to the destruction of acid rocks. Quartz enters as the main constituent in many metamorphic rocks, often performs sticks and veins, where well-formed crystals occur.

Quartz with inclusions of anthraxolite (similar to diamond). Photo: © А.А. Evseev.
County Herkimer, New York, USA. 3,5х2 cm. Similar to the Carpathian quartz.
Not characteristic for quartz form - a possible pseudomorph for diamond

Quartz ("Marmaroshian Diamond"). China. ~ 1.5 cm (Asia). Photo: © А.А. Evseev.

Brilliant, pure crystals of rock crystal are found in many areas of the globe. This species, as already mentioned above, was first met among the eternal snows in the Swiss Alps and was called "crystal". Good crystals come from Burg-d'Oisan in the department of Isère in France, from the marble quarries of Carrara in northern Italy and from the Marmarosh massif in Transcarpathia. Rolled rock crystal pebbles carried from the Alps to the Rhine were previously mined in Idar-Oberstein and were called "Reinstones" ("Rhine stones"). Unfortunately, this name was incorrectly applied to various fake precious stones carved from synthetic glass. Small shiny crystals received such misleading names as "White Island diamonds", "Cornish diamonds" or "Bristol diamonds" in the places of their discoveries. A similar material was found in Tanjore County, Madras in India, where it is used to make cheap jewelry crafts and is called "Vallum diamonds." In the valley of the Indus River, of such stones, necklaces are made; Here these stones are called "mari-diamonds". Japan supplies beautiful samples of quartz, especially "Japanese counterparts," in which two crystalline individuals are isolated, and directions parallel to the edges of the prisms are located almost at right angles to each other. Good rock crystal is mined in Madagascar and in various parts of the United States. A huge amount of excellent material used in optics and electrical engineering, supplies Brazil. Transparent pieces of quartz sometimes are so large that stone lovers give them the shape of balls.

Japanese quartz double. Brazil. .

Rock crystal (Japanese dv-k). South. Ural, Russia, the CIS. Photo: © D. Tonkacheev.

Quartz (Japanese double). Karabash, U. Ural, Russia, the CIS. More than 4 cm. Photo: © А.А. Evseev.

Brazil is also famous for its magnificent amethysts. The main area of ​​their extraction is in pcs. Rio Grande do Sul, from where it extends across the state border to Uruguay. Amethysts are also found in many deposits in the United States. Recently it was reported about the discovery of very large crystals in Dyo West in pcs. South Carolina. Material from Fort-Pix in pcs. Arizona acquires a green color when heated, reminding in this respect the "praziolite" from Montezuma in Brazil. These crystals are similar in their habitus with crystals from Sander Bay on Lake Verkhny. Good crystals were extracted from pebbles in Ceylon, and also mined in the Urals. The extraction of quartz was carried out in the prefectures of Etigo, Hawky and Iwaki in Japan. It is believed that the material that appears on the market in Africa comes from Tanzania; Other sources here are Zambia and Namibia. Among the Australian deposits, mention should be made of the Willu Station in the Ashburton district of Western Australia. In Ireland, pink mauve crystals were found in Kim Bay on the island of Ashill. Sarkestone is an amethyst found on the island of Sark in the English Channel; But for a long time here no longer find these stones, and the samples sold to tourists under this name are either imported material or imitation. Three magnificent faceted samples of amethyst are in the Minerals Gallery of the British Museum of Natural History. The largest of them, weighing 343 carats, has an oval shape and is found in Brazil. The other two were brought from Russia. One of them has hexagonal outlines and weighs 90 carats; Another, dense purple, has a rounded shape and weighs 75 carats. Excellent quality kerningors were formerly found in large numbers on the mountain of the same name in Scotland, but now it is rare. It is still highly pruned and widely used in this country as decorations, especially in the costumes of the highlanders. At one time it was possible to find chernogrom in a number of places in the central part of the Grampian Mountains. Individual crystals reached a weight of several tens of pounds, and one day a large amount of this stone was extracted from one large cavity in granites. Another field of brown quartz was Gotfell on the island of Arran.

A very large amount of smoky quartz, sometimes in the form of exceptionally large crystals, was found in the Swiss Alps. Smoky quartz, which becomes yellow when heated, was found near Córdoba in Spain. In the US, a beautiful kerphorhome is found on Mount Pikes Peak in the pc. Colorado; Excellent material was also found in a number of other deposits. Large crystals of smoky quartz and amethyst originate from the western part of Carroll County in the pc. New Hampshire. The right crystal, found in Stoneham in pc. Maine along with numerous smaller crystals, had a length of 117.5 cm, a thickness of 42.5 cm and weighed 230 kg. In Asia, good material comes from the Nerchinsk area and from Manchuria. Magnificent citrine is found in many Brazilian states, especially in pcs. Minas Gerais, Sao Paulo and Goias; Here citrine is often confused with topaz. It is claimed that yellow quartz, described as citrine, is found in many other deposits. It is said that citrine is found among the precious stones supplied from Madagascar. In England, the finds of citrine in Cornwall are described, and some colored quartz crystals from Gotfell on the island of Arran were also called citrine. However, here again it should be noted that most of the yellow quartz, given for citrine, was obtained as a result of heat treatment of smoky quartz or amethyst. Fine pink quartz is rare. It was mined in the valley of the river Zheqityniona in the Brazilian pc. Mipas Gerais; From the pegmatites of Namibia; Together with citrine and smoky quartz in Madagascar; In Goto in Iwaki Prefecture in Japan; In Bodenmais in Bavaria; In Piris in the pc. Maine and near Custer in the Black Hills mountains in the pc. South Dakota in the United States; in the Urals.

Silicon is one of the most important macroelements. In the body it participates in the formation of connective and epithelial tissues, promotes the growth of hair and nails, stimulates phagocytosis. It is contained in the form of various compounds involved in the formation of solid (skeletal - connective tissue in bones) parts and tissues. Deficiency of silicon can develop with insufficient intake of an element in the body (5 mg / day or less).

In the human body contains about 1 g of silicon. In the body, about 4% of the total amount of silicon is absorbed. Among the internal organs, the leader is the thyroid gland - it accumulates up to 310 mg of silicon. The content of silicon in the brain tissues is 0.001-0.01%, they are rich in a solid (external) cerebral membrane, the cerebral cortex (covers the brain), and the cerebellum. The concentration of silicon in the brain depends on the state of the central nervous system (the brain), for example, when the central nervous system is excited, its amount decreases in the brain tissues, and when it slows down, it increases (psychiatry).

Soluble compounds of silicon are absorbed in the thin and duodenum. According to the spectral analysis, in the daily products isolated by a healthy human body, the content of silicon is 4.7%. An additional method is recommended for Alzheimer's disease, osteoporosis, cardiovascular diseases. Silicon is well absorbed together with molybdenum, magnesium, fluorine, and also fiber (carbon).

With any chronic and acute pathology, the need for silicon increases, and an increased intake of this element leads to an improvement in well-being and helps the body cope with the disease. Silicon is also indicated for maintaining the health of nails, skin and hair. The emergence of many pathological processes, including cancer, atherosclerosis, tuberculosis, diabetes, goiter, dermatitis, stones in the urinary tract, is often associated with impaired metabolism in the body of silicon compounds.

Signs and symptoms of insufficiency. Loss of blood vessels of elasticity (which leads to acceleration of aging processes), caries and periodontitis, brittle nails and hair loss. The medicinal properties of silicic water are widely known. Silicon water is a simple means of replenishing the concentration of this vital substance in the body. One of the most natural sources of silicon is blue (containing radioactive uranium), medicinal (yellow-brown, with gold and iron), food clay (white, kaolin-kimberlite).

The increased content of silicon in the body is found in workers of the mining industry in contact with asbestos, quartz, aerosols, cement, glass, etc., in areas with an excess of silicon compounds in water and in air. Systematic inhalation of dust containing free silica at high concentrations leads to the development of silicosis (rock crystal) - a disease of stone cutters. Manifestations of excess silicon: pulmonary fibrosis; urolithiasis disease; Malignant tumors of the pleura and abdominal cavity.

ADR 4.1
Highly flammable solids , self-reactive substances and solid desensitized explosives
Risk of fire. Flammable or combustible substances can ignite from sparks or flames. May contain self-reactive substances capable of exothermic decomposition in the case of heating, contact with other substances (such as: acids, heavy metal compounds or amines), friction or impact.
This can lead to the emission of harmful or flammable gases or vapor or spontaneous combustion. Containers can explode when heated (over-dangerous - practically do not burn).
Risk of explosion of desensitized explosives after loss of desensitizer
Seven vertical red stripes on a white background, equal in number, ADR number, black flame

ADR 8
Corrosive (corrosive) substances
Risk of burns from skin corrosion. They can react violently with each other (components), with water and other substances. The substance that spilled / crumbled can emit a corrosive vapor.
Dangerous to aquatic environment or sewer system
White upper half of diamond, black - lower, equal, ADR number, test tubes, hands

• Ghetchellit - "New Almaden blend" - arsenide and antimony sulfide (modern sulfosol)
• Antimony is a toxic metal (semimetal) , widely used in metallurgy, medicine and engineering
• Zirconium - a rare and undiscovered metal and the most dangerous precious stone in oxide and salt
• Gold - yellow dangerous and poisonous metal of modern accurate digital and cable technologies
• Sulfur is a golden-yellow toxic substance and a sign of active volcanic activity
• Cadmium is an undisputed toxic silvery metal unknown to a wide range of people
• Lead - a poisonous gray imitator of metallic silver and toxic metal blende
• Arsenic is a classic poison of medieval and modern poisoners and medicine in medicine

Poisonous and radioactive dangerous stones and minerals

^** - poisonous stones and minerals (mandatory check in the chemical laboratory + explicit indication of toxicity)
^** - radioactive stones and minerals (mandatory check on the standard dosimeter + ban on open sales in case of radioactivity exceeding 24 milli / g / h + additional measures of population protection)

Catalog of minerals and semi-precious stones of the world by groups

^** - poisonous stones and minerals
^** - radioactive stones and minerals