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Gem drawing. Minerals and rocks. So what is a mineral

There are many types of natural stones, they are classified by deposit, structure, composition. Each of them is unique and beautiful in its own way, which is why many are used in jewelry and applied art. Some people appreciate them for their beauty, others - for qualities that are useful from a practical point of view, others are attracted by their medicinal and magical properties.

What types of classification of natural stones are accepted by mineralogists and jewelers?

There are several signs by which all stones are classified. The Kluge and Bauer system is used more often. German scientist-mineralogist Kluge compiled a list of 5 groups of minerals. Three include precious specimens (diamonds, topaz, opals, garnets, tourmalines), and two are reserved for simple gems. Bauer made changes to the system, adding non-precious crystals and organogenic formations.


In Russia, jewelers use the Bauer's classification of stones, supplemented by the scientist Fersman. According to the description and definition, natural stones are divided into classes, gems for crafts are separately distinguished. Kievlenko in 1973 proposed to take into account the price of natural samples and their purpose. Since that time, the systematization has included jewelry, jewelry and ornamental and ornamental gems. The last additions were made by Melnikov almost 10 years ago. He added adjustments to the Kievlenko classification, including the functionality of minerals.

Table of varieties of stones for use in jewelry

Natural stones are usually divided into mineral and organic (while all of them belong to inanimate nature). Jewelers subdivide them into precious, semi-precious and ornamental. Precious minerals are called transparent specimens that have a diamond luster, hardness and transparency. Weight unit - a carat weighing 0.2 grams.


 Sapphires

The remaining 2 varieties are measured in grams, they include 2400 stones, including sulfides. Ornamental are opaque natural fossils with a soft structure. Usually they differ in pattern or color and gloss. The table contains a list of formations by grade.

Group nameClassRepresentatives of a natural mineral
Jewelry GemsIRubies, emeralds, sapphires (blue), diamonds
IISapphires (orange, green, purple), black opal, alexandrite and noble jadeite
IIISpinel, opal (white and fire), topaz, tourmaline, rhodolite, aquamarine
IVChrysolite, zircon, pyrope (green and pink), malmandine, amethyst, citrine, sun stone
Jewelry and semi-precious stonesILapis lazuli, jade, amber, rock crystal (colorless and smoky), malachite
IIAgate, obsidian iridescent, amazonite, rhodonite, opaque spars
Ornamental Fossils- Jasper, colored marble, fluite, selenite, pegmatite, jet, onyx, listvenite

Pegmatite

Part of the crystals used in jewelry is shown here. There are about 100 varieties of minerals, but only 20 of them can often be found in different products.

Species by origin and composition

List of organic entities

In each classification, there is a subdivision of stones and minerals by origin. There are organic, endogenous, exogenous and metamorphic formations. They differ from each other in composition, density, shades, formation time and other characteristics.


 Ammonite

Fossils of various types are classified as organic stones, once living organisms or resulting from biological processes. The group's representatives have the following names:

  • ammonite;
  • nacre;
  • coral;
  • pearl;
  • amber;
  • Ivory;
  • jet;
  • belemnite (or damn finger);
  • petrified wood.

 Belemnite

Each of them has a unique history of origin and properties. It took several millennia to form part of the stones that were once part of the living world. However, many are able to form within 7-10 years.

Endogenous stones

The endogenous process takes place in the bowels of the earth's surface. Stones are formed from a silicate fiery liquid melt called magma. There are many representatives of the group, but not everyone is used in jewelry. Often, the choice of specialists falls on quartz, which is shown in the photo. It is hard, resistant to water and alkalis.


 Quartz

Exogenous formations

An exogenous process is characteristic of the surface of the earth's crust; rocks are mined on land and in the sea. For the formation of crystals, weathering is necessary, after which several groups appear at once: hydromica, kaolinite, halite, opal, sylvin. Some are the result of marine life and plant life. All exogenous formations have properties that are different from other minerals. They are relatively soft, do not tolerate contact with water and acids.

Metamorphic minerals

The formation of metamorphic types of minerals occurs under the influence of certain factors in the earth's crust. Some require high temperatures and pressure drops, while others require magmatic gases or water. To start the process, previously formed exogenous samples are required. As a result of metamorphic formation, minerals become stronger and acquire a high density.


How are stones classified by structure?

The classification of minerals includes many items, including structure. Jewelry varieties have a crystalline structure. The cost of a natural mineral depends on refraction, transparency, hardness and color. Craftsmen pay attention to the brilliance of the mineral and the play of shades, density and the possibility of cutting.

In addition, there are amorphous and metaminctic minerals - passing from a crystalline state to an amorphous one.

How are minerals divided according to the place of their extraction?

Fossils are mined in almost all corners of the world, but some can only be found in specific countries.


 Pyrope

The most common suppliers of stones are: Europe, China, Thailand, Japan, America. Certain elements of rocks can be found in the following countries:

  • pyrope - in the Czech Republic;
  • ruby and jadeite - in Burma;
  • sapphire, various types of quartz and emerald - in India;
  • turquoise, jade, pearls - in China;
  • amber, lapis lazuli, jade and diamond - in Russia;
  • turquoise, chrysolite, beryl - in the USA;
  • opal, quartz - in Mexico;
  • Eilat stone - only in Israel;
  • tanzanite - only in Tanzania.

France, Israel, USA, Sri Lanka are considered to be processing centers for representatives of inanimate nature. In Russia, similar enterprises are located in Moscow, Irkutsk and Sverdlovsk.


 Lapis lazuli

Unusual properties of minerals

The scientific characteristics of minerals do not allow them to be considered alive, although many people believe that stones have the ability to heal or provide magical assistance. However, beautiful minerals can be both beneficial and harmful. Fortunately, such fossils are few and far between. There are rocks with the inclusion of luminous and soft stones, from which jewelry is not made, but is used in other areas.

Glowing stones (names and photos)

A mineral called "fluorite" glows in the dark, as you can see in the photo. It can be of any shade: from transparent white to purple or dark purple. It starts to glow if you warm it up a little in the palms of your hands.


 Fluorite

Scientists from Michigan recently discovered sodalite stones that glow. They are neither precious nor semi-precious. However, this does not prevent them from being used to decorate the landscape.

Poisonous minerals (photos and description)

The sulfides are beautiful but deadly. It is helpful to know which sulfides are harmful minerals. Galena is the rarest sulfide mineral with an interesting structure (see photo). People who came into contact with toxic galena without protective equipment were struck by serious pathologies. Often sulphide crystals are selected out of curiosity, but experts try to bypass the stones. Professionals are familiar with respiratory problems after inhaling hazardous galena dust.


 Galena

Another mineral that looks attractive but is harmful is called chalcanthite. Consists of copper, sulfur and water - the components form a toxic mixture. A small dose of a hazardous substance, if it enters the human body, causes the failure of internal organs.

Some stones are irradiated, due to which they change their shade and properties. Experts believe that even after the removal of radioactivity, such rocks remain dangerous. Irradiation is expensive and is rarely used.

Soft stones

In the first place is the natural talcum stone, which is easy to scratch and crumble. However, other sulphides are difficult to break but can be cut. In second place is a mineral called asbestos, from which fire-resistant tablecloths or napkins were previously made. Also known are travertine, limestone, Dagestan shell rock, which are used to build houses or decorate walls.

Inanimate nature has more than 4 thousand stones, the characteristics of minerals are becoming more detailed. Unusual facts about them leave no one indifferent:

  • the "cat's gold" pebble shown in the photo below can be easily confused with real gold in appearance, but it has no value;

 Pebble "cat's gold" (pyrite)
  • in nature there are "watermelon" minerals tourmalines, which have a pink core and a green edging;
  • the diamond is so strong that it can scratch anything;
  • crystal, citrine, morion, aventurine - this is one and the same stone called "quartz", which has different brilliance and colors;
  • to search for an emerald in 1 carat, they process up to 20 tons of soil;
  • the prices of precious gems go up as they become fewer.

Mineralogy has over 6 thousand minerals, and every year at least 10 new ones are added to this number, which were previously unknown to people. Their beauty can be judged by the fact that at all times there were connoisseurs and collectors who could, without hesitation, pay the cost of a fortune for one such piece for their collection. The most beautiful of them have always been associated with intrigues, and sometimes with crimes, to which people were pushed by greed or the power of precious minerals that always attracted people to itself.

It got its name from the town of Spessart, located in Bavaria. It was in this area that spessartine was first discovered, which was considered at that time the rarest mineral in the world. Later it was found in many countries of the world on different materials, but has not lost its value.

Spessartine belongs to the pomegranate group, in which it stands out in various shades of orange. Due to the presence of small bubbles of gas or liquid, the material looks especially mysterious.

In jewelry, it is used exclusively as a collection material, so not everyone can afford to have spessartine jewelry. The largest specimen is located in the United States, it weighs 109 carats and amazes everyone who sees it.

This mineral from the group of copper arsenates is rare enough to be expensive. It was first discovered in England at the end of the 19th century and immediately gained popularity for its exotic appearance. Beautiful rosettes are composed of interconnected small crystals with a pearlescent or glossy sheen, which resemble fantastic blue asters from other planets.

It could have become an ideal material for jewelry, if not for one property: when heated, it begins to emit an unpleasant odor, reminiscent of the smell of garlic, therefore, clinoclase is not used in jewelry.

If all other minerals are found in the bowels of the earth, then pearls are born in the water element. This happens after a grain of sand gets inside the soft tissues of the sea mollusk. To get rid of irritation and scratches, the body of the mollusk begins to envelop a grain of sand with mother-of-pearl. The longer this process lasts, the larger and more valuable the jewel will be.

The cost of a pearl determines not only its size, but also its shape, color, shine. Sea pearls are also expensive because, under their own weight, they fall to the seabed, from where it is very difficult to get them. Those pearls in products that can now be purchased in jewelry stores are of artificial origin: grains of sand are planted in a mollusc using tools. To get a finished pearl, you need to wait a couple of years, after which it will have a decent size.

Black pearls are considered especially expensive, which can only be obtained in Tahiti from a certain type of shellfish. However, the most expensive 203 gram pearl was cream in color, and the price for which it was purchased was $ 12 million. Her mistress and connoisseur was the magnificent Elizabeth Taylor.

The life of a pearl is not as long as that of other precious items: after 100-150 years, it begins to fade and loses its original beauty.

This gem always takes pride of place at exhibitions of stones, since it is simply impossible not to notice rhodochrasite and to pass by such beauty. The sonorous name from Greek translates as a painted rose. It looks like this flower not only in color, but also in an interesting structure.

At one time, Rhodochrasite amazed the Incas with its beauty. They saw in him the embodiment of the blood of their ancient rulers, which was frozen in this mineral. In addition, it was actively used for practical magic.

Rhodochrosite has amazing strength, so it cannot be cut. Despite this, jewelry is made of it, it is just that raw elements are placed in them, which often bypass even gold in cost.

In order for this gem to form, a temperature of over 450 ° C is required, therefore vast ruby ​​deposits are located at a great depth: more than 10-30 km.

The cost of a ruby ​​depends on the color and the presence of inclusions. An ideal stone should be free of these inclusions, as they affect the gloss intensity of the surface. For a ruby ​​to acquire its beauty, the skill of a jeweler is very important, who can make a beautiful cut, highlighting the dignity of the extracted material.

This stone has a very rich color and completely retains its color under artificial light sources, that is, it will look equally beautiful both in sunlight and indoors.

Most often, untreated emeralds contain a network of cracks and irregularities on their surface, but after processing all the defects disappear without a trace. Those gems that are initially endowed with an impeccable structure are highly valued - from 8 thousand dollars per 1 carat. It is in this form that these unsurpassed gems go to auctions, where collectors and connoisseurs buy them. The most expensive emerald "Theodora" weighing 1.87 carats was purchased for 400 million dollars. Until the moment the find was processed, its weight was 28 kg.

In the XIV century, near Yekaterinburg, a gem was discovered with a unique property: it radically changed its color depending on the lighting.

The name alexandrite was given in honor of Tsar Alexander II, since it was he who was presented with such an unusual mineral as a gift on the day of majority of the crowned person.

The shades and colors that a stone can display span a significant portion of the spectrum, from blue-green in sunlight to purple in artificial light. There are very rare specimens with an olive tint.

Scientists explained that the color of alexandrite changes due to the presence of chromium oxide impurities in it, which refract rays in different ways. Since this beautiful gem is extremely rare in its pure form, they often seek to forge it, therefore most of this material is fakes.

Jewelry is practically not made from it, since almost all items are sold out for collections of precious stones. In addition, alexandrite is credited with medicinal properties such as purifying blood and strengthening blood vessels. It is believed that an abrupt color change could indicate a spike in a person's blood sugar.

It is this stone that is most often used to decorate wedding rings all over the world. A diamond is made up of a single element in the periodic table - carbon. Until now, scientists cannot come to a consensus about when and how exactly this mineral was formed, since the formation requires the highest pressure and temperature. These conditions are met at great depths, but the stone is found on the surface. The age of each diamond ranges from 900 million to 2.5 billion years. Their density is so high that a ray of sunlight during the passage of the crystals halves its speed.

Diamond is more often than other jewelry stolen in all banks of the world, and the largest number of crimes is associated with it. The last high-profile robbery took place in 2007, when a thief entered the trust of bank employees, periodically treating them to chocolate. The value of the diamond that he was able to steal from the safe is $ 28 million.

In addition to the transparent stones we are accustomed to, which do not have color, there are also green, blue, yellow, red and pink diamonds, which are even more valuable. The most beautiful is the red diamond: a couple of years ago, a specimen weighing 0.97 carats was purchased for 1 trillion. dollars.

It is one of the minerals that people mention in their oldest chronicles. Red beryl is found even in the Bible: it was part of the divine stones, with the help of which Heavenly Jerusalem was built.

Red beryl gained particular popularity during the Middle Ages, as it was often used to inlay icons, altars, and church items. Jewelers could not ignore the beautiful stone either: they made seals for royals, massive rings, earrings, pendants, etc. from it. time of the most important events and great holidays.

In the 16th century, a bloody war broke out between the Spaniards and the Indians, during which the Spaniards tried to take possession of beryl, sacred to the Indians. However, the beauty of red beryl is no less appreciated now: the cost of the processed material is from 10 thousand dollars per 1 carat.

The beauty of this gem does not lie in the way the rays of light are reflected from it. On the contrary: fire opal seems to absorb light. It looks like a fire is burning inside the stone, which gives it a kind of glow.

This property is provided by an interesting structure: the material consists of special balls that are frozen in a strictly defined order. Fire opal appears at a rate of 1 mm in 2 thousand years. Up to 1/3 of water is present in the structure, therefore, when heated or over time, it can become lighter due to evaporation of moisture.

The beauty of this gem attracted people at different times: among the Romans it was associated with tears of happiness of the gods, among the Indians - with the placers of the rainbow goddess, among the Arabs - with fragments of lightning. The demand for fire opals has always been great, so they were hunted, looked for and were ready to sacrifice their lives for the possession of these minerals.

One of the most coveted pieces in any private collection is a stone with a huge range of colors and overflows. This mineral was a favorite among the crowned persons, therefore many representatives of royal regalia from Russian emperors and European rulers to Tamerlane were its fans.

There are one-color or polychrome forms, in which different colors are alternately combined, and there may be clots with a colored core. With strong heating, tourmaline becomes even more beautiful: brown specimens turn into rich pink, and dark green ones acquire a noble emerald color. Tourmaline has an interesting feature: when heated or rubbed, it becomes electrified.

This mineral became especially popular thanks to the great jeweler Faberge: during the incrustation of his works, he often preferred tourmaline, which can still be seen on most of the jewelry he created.

The name of the mineral was given by the philosopher Pliny the Elder. He believed that aquamarine is beautiful and clean, like sea waters, and it is difficult to disagree with this opinion.

This stone has always been used as a decoration, but some of the aquamarine crystals are the best interior decoration in their own right. So, in St. Petersburg there is a crystal, which is 125 cm long, and in Brazil, a specimen weighing 110 kg was found on the seabed.

In addition to its beauty, aquamarine also has medicinal properties: its action as a biostimulant helps to strengthen the body, save from seasickness, restore vision and improve a person's condition during allergies.

Aquamarine is not only a beautiful, but also a very fragile material, so jewelry with it is not suitable for daily wear: they can simply be crushed by carelessness. But during special occasions, he will perfectly emphasize the solemnity of the moment.

The variety of beautiful stones and minerals that the bowels of our planet give us is inexhaustible. Among them, you can find bright saturated colors or noble almost transparent specimens. Gems have a strange power of attraction, and the one who once saw them can never be indifferent to such beauty.

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Forget blue sapphires and ice diamonds - minerals can be just as beautiful, expensive and rare.

Opal contra luz

"Contra Luz" translates as "against the light." If you look at the stone from a certain angle, you can see the underwater world, distant galaxies, volcanic eruptions and the birth of new stars.

Fire opal

When you hold a fire opal in your hands, it seems that it is a drop of red-hot gold.

Black opal

Refraction of light reveals the secrets of the birth of a new universe. A very rare and very expensive mineral.

Opal fossil

Resembles the petrified shell of an ancient snail.

"Empress of Uruguay"

The world's largest cutaway amethyst geode sparkles in all shades of black, purple, lilac. The game of glare involuntarily evokes associations with a portal to the endless Universe. By the way, outside the geode is an inconspicuous black stone.

Boulder Opal

Algae sway inside the translucent stone, and multicolored fish swim melancholy in the water warmed by the sun's rays.

Fluorite

Fluorite in translation from the Latin fluor - "flow". Such an unusual name was given to the mineral for its unique color: emerald green smoothly flows into pale lilac and dark purple.

Bismuth

What is it? Alien computer, chip or microcircuit? No, it is a dense and soft metal. When interacting with water, it oxidizes and becomes covered with a film that plays with the colors of the rainbow. Farmed bismuth has clear geometric shapes.

Titanium quartz

Multicolored crystals are extremely popular at auctions: who would have thought that the rainbow mineral was the work of scientists?

Rose quartz geode

Are the cosmogonic myths that the Universe originated from the World Egg, not an invention of the ancients? The regular rounded shapes of the geode, created by Mother Nature, the amazing mixture of light and color, inspire philosophical reflections on the mysteries of life.

Chrysocolla in malachite

Chrysocolla is a hydrous copper silicate that gives ornamental malachite a delicate bluish tint.

Azurite

Sparkling azurite shimmers in all shades of blue.

Scolecite

Coldly sparkling with facets, this unusual flower will be a worthy gift for the Snow Queen. Perhaps he will melt the heart of an unapproachable beauty.

Watermelon tourmaline

The name sherla speaks for itself: the bizarre color combination resembles a juicy slice of watermelon. Due to its polychrome (multicolor) nature, the mineral is classified as a gemstone.

Burmese tourmaline

Magical reflections of burgundy, rich sparks of pomegranate and pink shimmer mysteriously. Pendants are made of teardrop-shaped minerals of stunning beauty.

Crystalline bismuth

One gets the impression that this is an artificial city with skyscrapers and suburban houses ... No, this is crystalline round bismuth - space for a jeweler's imagination.

Realgar on Calcite - Ice and Fire

In the arms of cold ice rests a raging flame that is beyond the control of anyone - flashes of crystals will soon melt the lump and break free! Or not? Realgar and calcite will be together forever.

Cobaltocalcite

A rare pink mineral with an unusual color, highly prized by collectors. Transparent stones are used for cutting.

Uvarovite

The main photo shows a sharp, daring, crystal clear, perfectly correct mineral, which arouses a genuine interest of collectors and jewelers, as it is ... garnet. No, not the usual blood-cherry, but deep green. The second name is the Ural emerald.

Crocoite

In translation, "crocoite" means "saffron". Indeed, the elongated crocoite crystals look like dried crocus flowers.

Rhodochrosite

The second name is “rose of the Incas”. The Incas believed that the blood of their ancestors turned into stone, which is capable of giving strength to the people. It is considered one of the most ancient ornamental stones.

Pink rhodochrosite

Another variety of the Inca rose is a matte pink mineral.

Botswana (striped) agate

It seems that the Creator-artist ran a brush with watercolors - there is no other way to explain these fantastic stains from milky white to jet black with a glaze of dark blue, dirty purple and azure blue ...

Alexandrite

It is able to change its shade depending on the time of day and lighting, therefore it is appreciated by jewelers. It is about this stone that they say that it is a ruby ​​in the evening, and an emerald in the morning. The amazing property of changing hue is called pleochroism.

Ammonite

A variety of many-sided opal, on the smooth surface of which you can see the imprints of algae from the Proterozoic era and interspersed with unprecedented protozoa ... But this is just a fantasy! Opals can be looked at endlessly, finding more and more interesting landscapes with each passing second.

Cornelian

The stone, which resembles solidified lava, really has a volcanic origin: being formed in a crater or lava bubbles, it is saturated with the power of earth and fire.

Bentoite

The union of titanium and barium silicate gave life to a very rare mineral, which is not inferior in beauty to precious sapphire.

Polychrome tourmaline

The mineral shimmers in more than five shades: from pale pink to red, from red to green. Translated from Sinhalese means "attracting ash" and "magic multi-colored stone".

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In translation from the medieval Latin language minera means ore. A mineral is a chemically and physically independent solid that has a relatively homogeneous composition. It arose as a result of the physical and chemical processes of natural origin occurring in the bowels of the Earth and other planets. It usually refers to a constituent part of rocks, meteorites or ores. Most of the well-known stones received their names in antiquity - at the time when the science of mineralogy did not yet exist, but people were already actively using many types of minerals.


The history of the use of mineral raw materials goes back many centuries: the Stone Age came long before the Bronze and Iron Age. At this time, the main household tools and weapons were made precisely of stone. Yes, people still used wood and bone, but the century was still called stone, and this is not accidental, it was he who made it possible to make the so necessary leap in development.

Since ancient times, people have been attracted by minerals, their enchanting beauty and mysterious power do not leave anyone indifferent even now. The variety of shapes and colors, the splendor of the shades created by nature are mesmerizing. Ancient people worshiped precious stones, considering them to be symbols of immortality. And this is not surprising, because human generations go into oblivion one after another, everything flows and changes, only stones remain forever. These things for a modern person are not only luxury goods and a great way to invest capital. They are a source of inspiration for poets and jewelry for women, a subject of research for scientists and a working material for jewelers.

People believe in the magical power that minerals have in them. Scientists know how many mysteries not disclosed by science are hidden in the strata of rocks and in the depths of the earth's crust. For some it is a source of healing and inner strength, for others it is an object of admiration and admiration. But they do not leave anyone indifferent. Immerse yourself in these dazzlingly beautiful gifts of nature, so varied and delightful that you can endlessly admire them. Find out more about the treasures that lie right under our feet!

So what is a mineral?

Minerals are called homogeneous natural bodies, which are chemical compounds of a certain composition, having a crystalline structure and formed as a result of geological processes. They are components of rocks.

Rocks are masses or aggregates of one or more mineral species or organic matter formed as a result of natural processes.

These are the materials that make up the earth's crust. There are hard, loose, soft and consolidated rocks.

There are some other concepts related to the above. A mineral variety is a group of minerals that have small differences in chemical composition and physical properties. A mineral individual is understood as a mineral body separated by an interface.

Origin of minerals

Genesis is the process of mineral formation. Such processes are divided into three groups, depending on the source of energy.

1. Magmatogenic (hypogenic) processes

Formation occurs by solidification and crystallization of magma.
This solution-melt, consisting mainly of silicates (silicon compounds) and containing all chemical elements, either overcomes the resistance of the overlying rocks and pours out onto the surface, or remains in the depths and cools and crystallizes there. Accordingly, products are classified into effusive and intrusive, respectively.

Since any magma has a predominantly siliceous composition, silicates (siliceous minerals) are formed there. Many of them are rock-forming minerals that form granites, syenites, diorites, and other crystalline rocks. They are largely represented by feldspars, granites, micas, hornblendes, olivine, etc. In the process of their formation, the transition of Si, Al, Ca, Fe, Mg, Ti, K, Na, H2, O2 from magma to residual melt occurs.

When intruding into the earth's crust, the magma temperature is about 1200 ° C. By the end of crystallization, it decreases to 500 - 600 ° C, and at a given temperature, residual melt is introduced into the cracks of the rocks, forming pegmatite veins.

Part of the volatiles gets into the crystallized rocks through cracks. They act on the constituent minerals and transform them. This is how greisens, tungsten, molybdenum, tin and rare metal ores are formed in granites.

With a further decrease in temperature, hydrothermal solutions are released. They form deposits of gold, zinc, copper, silver, uranium, lead, antimony, mercury, tin, arsenic.

2. Metamorphic processes (endogenous)

They imply changes in minerals in the depths under the influence of pressure and temperature. These phenomena occur in connection with a change in the geological setting and the initial occurrence of rocks.

Regional and contact metamorphism is distinguished. Processes of the first type affect large areas and occur at significant depths. This is accompanied by the formation of shales and gneisses. Contact metamorphism consists in the impact of magma (especially granite) when intrusion into the strata of marl and limestone. As a result, they turn into marbles and skarns. Deposits of iron, tungsten, molybdenum, tin, cobalt are sometimes associated with them.

3. Exogenous processes

These phenomena are due to external factors associated with the energy of the Sun. They occur at normal pressure and low temperatures near the earth's surface. They consist in the fact that rocks and minerals exposed and lying at shallow depths undergo weathering (destruction) under the mechanical and chemical effects of water, sun, wind, organisms, etc. Some of the destroyed rocks and minerals are carried away, some remain in place, forming placers of gold, platinum, zircon, diamond, garnet, tin, magnetite, tungsten derivatives, etc. Many rock-forming minerals are destroyed and dissolved. Their salts are carried by waters, and in arid regions they precipitate, forming deposits of gypsum, sodium and potassium salts, and mirabilite.

That is, exogenous mineral formation occurs as a result of the mutual action of factors of the atmosphere, biosphere, hydrosphere on minerals on the Earth's surface. New minerals formed in this way from the original are called hypergene.

In addition, there is a biochemical subtype of exogenous mineral formation. It consists in transforming the remains of organisms and their vital activity. As a result, fossil fuels, chalk, limestones, native sulfur, some brown iron ore, phosphorites are formed. Feldspars, plagioclases, hornblendes, etc. are very common.

Classification

Structural-chemical classification is generally considered to be the main one.

So, crystal chemical includes 9 types:

  1. Silicates. Silicic acid salts. They are represented by the most common rock-forming minerals in the earth's crust (more than 90% of its mass), which are part of all types of rocks. They include about 800 species, divided on the basis of the structure of the crystal lattice into 6 subtypes: island, ring, chain, ribbon, layered, frame. These are feldspars, plagioclases, hornblendes, etc.
  2. Carbonates. About 80 items represented by carbonic acid salts. The most common among them are magnesite, calcite, dolomite.
  3. Oxides and hydroxides. This includes about 200 mineral compounds with oxygen and a hydroxyl group. They are subdivided into compounds with silicon (quartz, etc.) and compounds with metals (hematite, limonite, etc.). They make up about 17% of the mass of the earth's crust.
  4. Sulfides. About 200 compounds with sulfur (pyrite, bornite, cinnabar, etc.).
  5. Sulfates. There are about 260 mineral species represented by sulfuric acid salts (gypsum, barite, anhydrite, etc.).
  6. Haloids. Halic acid salts. Includes about 100 items (halite, sylvin, fluorite, etc.).
  7. Phosphates. Phosphoric acid salts, including apatite and phosphorite.
  8. Tungstates. Salts of tungstic acid (wolframite, scheelite, etc.).
  9. Native elements. Includes 45 items, consisting of one element (gold, sulfur, diamond, etc.).

Structural-chemical

There is also a structural-chemical classification close to this. According to it, there are two types: inorganic and organic minerals.

The former include the following classes:

  • native elements and intermetallic compounds;
  • nitrides, carbides, phosphides;
  • sulfides, sulfosalts and the like;
  • halogen compounds and halogen salts;
  • oxides;
  • oxygen salts.

In terms of prevalence, minerals are divided into four types:

  • 1. Rock-forming. They make up the majority of rocks.
  • 2. Accessory. Often present in them, but usually up to 5%.
  • 3. Ore. They form significant accumulations in the form of ore deposits and contain industrially valuable components.
  • 4. Rare. Few or few.

There are three forms of being in nature:

  1. Mineral individuals. These are the constituent parts of aggregates, represented by crystals, grains, and other precipitates, separated by interfaces.
  2. Mineral aggregates. Accumulations of individuals of one or different minerals, which do not have clear signs of symmetrical figures. There are one- and multi-stage.
  3. Mineral bodies- aggregates of aggregates with natural boundaries. The sizes can be from microscopic to those comparable to geological objects.

In addition, the genetic classification discussed above is used.

Secondary minerals

This is the name of the minerals formed during metasomatism, during the weathering of other minerals and rocks, that is, during processes that transform already formed rocks. Eskala (Finnish petrographer) called these minerals posterior (in Latin - subsequent).

These in igneous rocks include minerals: epidote, zoisite, serpentine, muscovite, tourmaline, talc, calcite ... In other words, all hydro-acid and carbonate compounds that cannot be released from fiery liquid magma. But many minerals, generally formed directly during the solidification of magma, can be present in one or another rock and as a secondary mineral (for example, quartz, ore minerals, and others).

The distinction between secondary and primary formations is essential in petrography. The primary components illuminate the conditions of the genesis of the rock, and the secondary minerals make it possible to trace the course of certain changes and transformations that the rock has undergone.

Finally, minerals are categorized according to their practical importance, which is shown below.

Properties

Properties are divided into chemical, physical, optical, magnetic.

Chemical properties are determined by the elements that make up the composition: the chemical formula of the mineral. It is these properties that also determine the solubility of minerals and acids.

Physical properties are determined by the chemical composition and their crystal structure. Some of them appear depending on the crystallographic direction. Based on this parameter, they are divided into scalar and vector (the former depend, the latter do not). Density refers to scalar properties, hardness to vector properties, and crystallographic features.

Also, physical properties are classified into mechanical, optical, magnetic, luminescent, thermal, electrical, radioactivity.

Many parameters are used to determine minerals in the field (diagnostic properties). In addition to the main external characteristics, such as shape and color, hardness, separateness, cleavage, fragility, luster, fracture are used for this. Some minerals are diagnosed for flexibility, malleability, and toughness.

By mechanical properties, you can find:

  • fragile (main part);
  • malleable;
  • inflexible (among foliose and scaly);
  • brittle and flexible (fibrous minerals).

Fragility- the strength of mineral grains, manifested by mechanical splitting.

Among the physical properties, a very important indicator of minerals is hardness... On its basis, the 10-digit Mohs scale was created. In it, each value corresponds to a mineral (from talc to diamond). It should be borne in mind that for some mineral species this parameter differs for different sides (for example, for kyanite 5.5 and 7). This is due to the unequal density of the crystal lattice.

Cleavage it is the ability to split along crystallographic directions.

Tarnish- the presence of a thin colored or multi-colored film on a weathered surface. It is the result of oxidation.

Break this is an important diagnostic property. Thanks to it, the surface of the debris formed upon impact is characterized, forming surface features on a non-spun fresh cleavage.

Density it is the mass of a unit volume of a substance. It is also called specific gravity. By their density, minerals can be:

  • light - up to 2500 kg per cubic meter;
  • medium - from 2500 to 4000 kg per cubic meter;
  • heavy - from 4000 to 8000 kg per cubic meter;
  • very heavy from 8000 kg per cubic meter and more.

The density of a mineral directly depends on its composition, type of structure, the number of microinclusions and their nature, as well as on such phenomena as metamictity and hydration.

Specific gravity it is the ratio of the density of a mineral to the density of water. It is used to determine the unit mass and serves as a diagnostic feature for some classes. So, the highest value of this parameter is possessed by native metals and intermetallic compounds (for example, for gold it is 19.3 g / cm3), among the common minerals are oxides and sulfides, due to the presence of elements with a high atomic mass in the composition.

Optical properties

Colour. In some minerals it is definite, in others it is very variable. The latter can be explained by the presence of many modifications or polychroism. In the first case, due to the inclusion of impurities in the chemical composition, the mineral gets a different color. In the second, the crystals change color depending on the direction of the light entering.

  • White stone
  • Black stones
  • Red colors and gems
  • Orange stone
  • Yellow stone
  • Green stone
  • Blue stone
  • Blue stone
  • Purple stone
  • Lilac stone
  • Pink stone
  • Brown stone
  • Transparent stones

Line color. It manifests itself when scratching. The same as the color of the mineral in powder. Glitter is a light effect created by the reflection of a part of the light flux. Determined by reflectivity.

Refraction, polarization, dispersion characterize optical constants.

Magnetic properties determined by the content of ferrous iron.

Place of Birth

Large accumulations of minerals are called deposits. There are several classifications of them.

  • According to the state of aggregation of mineral substances, they are divided into gas, liquid, solid.
  • For industrial use: ore, combustible, non-metallic, hydromineral.
  • By the complexity of the geological structure: simple (group 1), complex (group 2), very complex (group 3), with small bodies, disturbed bedding, variability of thickness and structure, or uneven quality (group 4).
  • By location relative to the earth's surface: open, buried.
  • According to the conditions of formation: magmatogenic, metamorphic, exogenous.

You can learn more about minerals in the Mineral deposits section. We have descriptions of more than 40,000 locations around the world.

Application

About 15 percent of the minerals known today are used industrially. Some minerals are used to make various types of metals and some other chemical elements.

The use of certain types of minerals for technical purposes based on their physical properties:

  • hard minerals such as diamond, garnet or agate are used to make abrasive and anti-abrasive materials;
  • stones with piezoelectric properties such as quartz are used in the radio-electronic industry;
  • muscovite or phlogopite related to mica, due to the presence of electrical insulating properties, are used in radio and electrical engineering;
  • quartz or pyrophyllite - in the manufacture of ceramic products;
  • talc - for the production of lubricants and in the medical industry;
  • asbestos is used as a heat insulator;
  • Icelandic spar or fluorite is used in the production of optics.

Mineral raw materials are used in all industries. Whenever possible, the use of minerals is subdivided into ore and non-metallic. From the former, metal elements are mined, and from the latter, non-metallic raw materials for the production of construction, medical, chemical and other products.

Separately, it should be noted the aesthetic value of minerals. The stones used in jewelry are well known. They are even more used as ornamental raw materials and in their original form as exhibits in museums and collections.

There are value-based classifications. In accordance with one of them (VNII Yuvelirprom), they are subdivided into jewelry (diamond, pyrite, pearls, etc.), jewelry and ornamental (fibrolite, aventurine, azurite, etc.) and ornamental (obsidians, onyx, alabaster, etc.) ...

A similar classification is better known, according to which minerals are subdivided into precious, semi-precious and ornamental.

Such classifications are very arbitrary, since they primarily use aesthetic norms and several parameters (hardness, chemical composition, color, etc.) and there are no clear limits for any of them.

Popular minerals

Diamond is a cubic modification of carbon. In its pure (transparent) form, it is represented only by this element. Colored variants include various impurities. It is synthesized in several ways from carbon. It is the hardest mineral (10 on the Mohs scale). It is used in glass cutters, drilling equipment, jewelry.

Emerald- modification of beryl with an admixture of Cr3 + or oxides of V and Fe. It differs from it in green color and transparency. Found in crystals and intergrowths. Has a metamorphic origin. Possesses high hardness (7.5 - 8) and acid resistance. Artificial emeralds are characterized by lower density and refractive index. It is mainly used in the jewelry industry.

Ruby represented by a modification of corundum with an admixture of Cr3 +, Fe3 +, V3 +. Differs from it in red (purple, brown). Synthetic stones are obtained by growing from molten corundum. They are characterized by uniform color in contrast to natural ones. The second hardest mineral after diamond (9). It is used in instrument making, watch and laser technology, jewelry industry.

Sapphire- a kind of corundum, including impurities Fe3 +, Fe2 +, Ti. From a mineralogical point of view, sapphire is considered exclusively blue options, from a jewelry point of view - any color except red. Synthetic varieties are both pure (colorless) and with impurities (different colors). It is used in ophthalmology, dentistry, the production of glass and protective screens, the jewelry industry.

Alexandrite- a kind of chrysoberyl with an admixture of Cr. Differs in strong pleochroism (changes color from dark blue-green shades to purple), there are transparent variants. Hardness - 8.5. It is of magmatic origin. Artificial crystals are obtained in two ways. It is mainly used in the jewelry industry.

Pearl- biogenic education. Formed in the shells of molluscs. Does not apply to minerals, but includes aragonite. It is represented by bodies of a round or irregular shape with a hardness of 3 - 4. It can be of various colors (white, black, blue, yellowish, green, pink, etc.). There are glass and plastic imitations. It is mainly used in the jewelry industry.

Amber- biogenic formation, represented by fossilized tar of the Paleogene and Upper Cretaceous periods. It occurs in the form of amorphous formations with a hardness of 2 - 2.5. Color - from light yellow to brown, colorless, red, greenish, white. There are imitations made from natural resins and plastics. It is mainly used in the jewelry industry, less in pharmaceuticals, electronics, chemical, food processing, perfumery.

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