More and more often, fakes and poor quality goods are found in jewelry stores. On store shelves, there are jewelry with precious and synthetic inserts. Sometimes the buyer is deceived, and instead of a gem, he gets an imitation. The topic of artificial minerals excites the entire jewelry world. Even a gemologist will not be able to visually distinguish all products with a magnifying glass. How to recognize a gem without special education?

Artificial stones are:

• synthetic;
• ennobled;
• imitation.

Only in the laboratory can a synthetic crystal be distinguished from a natural one. The composition and structure of the minerals are identical. The basic physical properties of analogs are close to natural ones.

Gemologists also define refined crystals that undergo the following processing:

• staining;
• waxing (waxing / oiling);
• coating;
• heating (heating);
• filling;
• irradiation;
• whitening.

These data must be indicated in the certificate that is attached to the stone. In some stores, information is not conveyed to the client. The buyer can purchase a refined ruby, the cost of which is $ 5 ct at the natural price - $ 10,000 ct. The consumer can go to court, and such a transaction is regarded as fraudulent.

The Jewelry Confederation has developed a document for trade organizations. According to the prescription, special terminology accepted throughout the world should be used. . How do you know if a gem or not? This information can be obtained from the certificate.

In the civilized world, precious minerals are sold only with a certificate. To confirm the document, you can contact the laboratory.

The most prestigious logo on jewelry is Gübelin. The Swiss brand produces jewelry of the highest quality.

In jewelry stores, a certificate is issued for each stone. The document states:

• the size;
• Colour;
• proportions;
• purity;
• defects;
• cutting method;
• place of extraction.

The stores assure the buyer that all products are checked for compliance. How to determine if a stone is real or not, standing in front of a display case? All grown minerals are perfect.

How to identify a real stone yourself?

There are simple ways to define imitation:

• warmth;
• aurally;
• by weight;
• with a fingernail.

The mineral must be picked up and held. Natural material is cold and heavy. All minerals have inclusions. The product is viewed under different lighting conditions. To do this, use a magnifying glass, choosing a model with a magnification of 10 times. When viewed, the crystal is moved up and down to obtain a clear image at depth.

The gem can be wiped with a damp cloth. If there is a trace of paint on the fabric, do not buy jewelry.

The purity and perfection of the stone is a sign of a fake. Before buying a gem, you should study the following information:

• crystal shades;
• cutting methods;
• Place of Birth.

The synthetic crystal is determined using an ultraviolet flashlight. If the stone has a bright glow, then it is synthesized.

Natural stone scratches glass. There are ways and signs by which the authenticity of the crystal is determined.

Corundum

The physical properties of natural and synthetic corundums are similar. To recognize natural and synthetic rubies, sapphires, the presence of inclusions and cracks is important. How can you tell if a stone or glass is in front of you? A strong magnifying glass is used for this purpose.

Natural rubies contain rutile. The peculiarity of natural ruby ​​is its mottled color. Natural sapphires contain gas-liquid inclusions. A sign of their naturalness is the zonal coloration.

Features of synthetic corundum:

1. Gas inclusions of various sizes and shapes.
2. Curvilinear color distribution.

Natural sapphire resembles velvet in color. Fake spinel will be darker. If a beam is directed at a natural sapphire, it will be in the shape of a six-pointed star. Natural sapphire cannot be scratched with a fingernail or knife.

Emerald

If a natural crystal is examined with a magnifying glass, one can see cracks with gas-liquid inclusions. Sometimes they are mistaken for air bubbles in a fake.

A synthetic emerald can be tested by pointing an ultraviolet flashlight at it. If a stone is luminescent in an unnatural color, it is synthetic. Natural has a reddish-brown tint under ultraviolet light. This method is not accurate. Colombian emerald will not change its color.

How to tell if stone is natural or artificial? The natural mineral has clear edges, while the synthetic ones are worn out. Artificial crystal - with a yellowish tint.

Smaller emeralds are glued together into one piece. Other crystals are used for counterfeiting. This is how large samples are obtained by gluing a small emerald with synthetic spinel, beryl, quartz.

A quality emerald has a rich color. By the nature of the inclusions, the gemologist determines the deposit of the stone. Emeralds from Colombia are tinted. You can check this at home. The mineral is placed in water with washing powder.

Amber

There are several ways to determine the authenticity of amber:

1. Natural amber will always float on the surface of the saline solution (4 tablespoons per glass of water).
2. Apply a red-hot needle to amber. Smells like resin - natural stone, plastic - fake.
3. If amber is rubbed against natural fabrics, it becomes electrified. Finely cut paper will be attracted to the stone.

An ultraviolet filter is used for research. Transparent amber will luminesce blue and green. An opaque specimen gives a milky hue, while an untreated specimen gives a brown color.

Pearl

Natural formation extracted from shells is heavier than a fake. Pearls have an uneven surface, while imitation has a smooth surface. If two pearls are rubbed against each other, they cling.

One of the safest ways is to run pearls over your teeth. Natural stone creaks. If the pearl is dropped on the floor, it will bounce. Natural pearls can be scratched without leaving a trace. The price of natural, cultivated and imitation is different.

What stones do they imitate?

Glass and plastic are often used to counterfeit gemstones. With the help of these materials, they imitate such stones: carnelian, chrysoprase, turquoise and so on. Spinel and glass are used to counterfeit ruby.

Glued doublets are also used. Stones are combined with glass. How to distinguish a gem from a glass? It is easy to recognize a counterfeit with a magnifying glass. Bubbles will be located at the bonding point.

To imitate precious minerals, use:

1. Lower quality natural minerals.
2. Synthetic stones.
3. Glass.
4. Plastic.
5. Pressed crystals.
6. Composite stones (doublet, triplet).

It is difficult to determine the authenticity of a piece of jewelry without special knowledge. When buying a gem from a jeweler, it is best to contact an appraiser.

Mineral quality assessment

Gemological examination is a study of the authenticity of stones. Product quality control is as follows. The first assessment is visual. The gemologist examines the mineral with a magnifying glass. With this examination, the marriage is screened out:

• chips;
• scratches;
• scuffs.

There are specific inclusions for each mineral. The gemologist sends the product for additional research if he finds signs of:

• uneven color;
• bubbles.

The centers of expertise and assessment use the following devices:

1. Refractometer.
2. Polariscope.
3. Chelsea filter.
4. Jim the tester.

The extinction of the sample is determined using a polariscope. The gemologist will be able to immediately determine whether it is glass or mineral.

A refractometer measures the value of refraction, which is different for each material. An immersion liquid is used for research. Using a pipette, apply a few drops and cover with a protective glass. The readings are taken after 30 seconds. After that, it is compared with the data in the table and it is determined which mineral was brought for evaluation.

How to distinguish natural from artificial stone? The Chelsea filter helps to establish the origin of emeralds, sapphires and rubies. Some gemologists believe that the device has lost its relevance. Synthetic emeralds are difficult to distinguish even with equipment.

The Jim Tester measures the thermal conductivity of a mineral.

The laboratory determines:

• authenticity;
• origin;
• the presence of refinement.

The principle for evaluating a stone is called the "4C Rule". These are criteria such as weight, color, purity and quality.

Synthetic stones

Analogs are created specifically for jewelry, while the price of products is lower. The synthesized minerals have:

• maximum purity;
• high optical properties;
• color saturation.

In addition to analogs that have similar properties, scientists have created artificial stones - cubic zirconia and others.

The production of synthetic products is growing, and technologies are also improving. The buyer has the right to choose. Some want to have unique stones, others are only interested in external beauty. The consumer wants to receive the product that is indicated on the tag.

To determine minerals, there are many methods that require special instruments and laboratories (chemical, crystallographic, X-ray analyzes). At the same time, the simplest is known - macroscopic a method for determining minerals based on the study of their external features: crystal morphology, simplest mechanical properties (hardness, fracture, cleavage, etc.), optical (color, luster, transparency), etc.

In the macroscopic determination of minerals, the following rules must be adhered to:

determination of any characteristic is always carried out on the most recent split surface;

the sample must be slightly moved so that the light falls on it at different angles;

always compare the characteristics of the test sample with the corresponding characteristics of already known samples;

adhere to the following sequence of determination: hardness → gloss → cleavage → fracture → color in a piece → line → other properties;

immediately after determining each characteristic, you should write it down in a notebook;

always first determine all the specified properties, and only then begin the search for the corresponding sample in the literature (determinant of minerals).

Hardness is the most important property in the determination of minerals. The hardness of a mineral is its ability to withstand external mechanical stress. The hardness of minerals depends on the characteristics of their internal structure, as well as on their chemical composition. For example, graphite and diamond, although they consist of the same element (carbon), have completely different hardness, since their crystal lattices are not the same. On the other hand, limonite samples can also differ dramatically in hardness due to the different content of water molecules - the more water molecules, the lower the hardness. In this regard, it is important to remember that, firstly, hydrated compounds are always softer than anhydrous ones (like bauxite and corundum), and secondly, that there are a significant amount of minerals, the hardness of which is variable. The easiest way to determine hardness is to scratch one mineral with another. To assess the relative hardness, the Mohs scale is adopted, represented by ten reference minerals, the hardness of which is constant. In the Mohs scale, each subsequent mineral scratches all the previous ones (the higher the number of the mineral, the harder it is).

Talc - 1.

Calcite - 3.

Fluorite - 4.

Apatite - 5.

Orthoclase - 6.

Quartz - 7.

Topaz - 8.

Corundum - 9.

Diamond - 10.

There are no known minerals in nature that are located between corundum and diamond in terms of hardness. Therefore, for the practical determination of hardness, diamond is not required. To determine the hardness of the mineral under study, a smooth area is selected on its surface and, pressing hard, draw an acute angle of the mineral from the Mohs scale along it. If a scratch remains on the studied mineral, then its hardness will be less than that of the mineral on the Mohs scale; if there is no scratch, then the hardness of the investigated mineral is greater than the reference. The test is carried out until the investigated mineral falls in the interval between two minerals from the hardness scale, i.e. its hardness is not defined as intermediate between them or as equal to one of them. Some common objects are often used to determine hardness. So, the hardness of a soft pencil is I; nail - 2; glasses 5–5.5; steel needle and steel knife 6-7.

Shine mineral depends on its ability to refract and reflect rays and on the nature of the reflective surface itself. Distinguish between minerals with metallic and non-metallic luster. Metallic luster is inherent in minerals that reflect light like steel. Many sulphides, iron oxides, and native metals have such luster. Shine semi-metallic(metal-like) somewhat dimmer, it is characteristic of graphite. Glass luster is characteristic of the cleavage planes of many transparent or translucent minerals (calcite, gypsum, feldspars, facets of quartz crystals). Fatty luster (quartz fracture, nepheline) resembles the luster that appears on an oiled surface. Pearl luster is inherent in minerals, the surface of which shines like the inner (nacreous) surface of the shell (mica, talc). Silky the shine resembles the shine of silk fabric, characteristic of minerals with a fibrous structure (selenite, asbestos). Wax Some cryptocrystalline and amorphous aggregates (flint) have a luster similar to the luster of the surface of a candle. Matt gloss essentially means no gloss - the surface reflects light evenly dimly, like writing chalk. A matte sheen is inherent in earthy varieties with a finely porous surface (kaolin, bauxite). Simultaneously with the detection of gloss, it is convenient to determine the cleavage and fracture of the mineral.

Cleavage - the ability of minerals to split along planes. The cleavage planes coincide with those planes of the crystal lattice in which the adhesion forces between atoms are minimal. To detect cleavage, the mineral should be turned towards light so that some part of its surface reflects light into the eyes. If cleavage is present in the sample under study, then on the shiny surface you can see a lot of light reflecting plates, layering on top of each other, and forming a kind of ladder. All these shiny plates (cleavage planes) lie parallel and are separated by the thinnest dark lines. For many minerals, cleavage is expressed in several directions, mutually intersecting. For example, in micas (muscovite, biotite), cleavage is traced only in one direction. Halite and sylvin have three directions perpendicular to each other (cube cleavage). Sphalerite has six directions of cleavage planes. There are several types of cleavage: very perfect, perfect, average and imperfect. Very perfect cleavage is manifested in the fact that the mineral is very easily (with a fingernail, a knife blade) split in a certain direction into thin parallel plates with a smooth shiny surface (mica, talc, chlorite). Perfect cleavage is expressed in the fact that the mineral, with a light blow with a hammer, splits along even parallel planes (calcite, feldspar). Average cleavage is detected with a strong impact, while the cleavage planes can differ with some difficulty. Imperfect cleavage is detected with difficulty (apatite, beryl). These are practically minerals without cleavage. In the absence of sufficient skill, cleavage planes can sometimes be confused with crystal faces. Keep in mind the following:

minerals usually shine more strongly on cleavage planes than on crystal faces and any other fracture surfaces;

in the cleavage plane of the mineral, one should always find several parallel plates, successively layering on top of each other (like steps).

Simultaneously with the determination of cleavage (and gloss), a fracture of the mineral can be detected.

Break ... When splitting different minerals, you will notice that the resulting surface is different. Depending on the nature of this surface, fractures are of the following types:

granular - the surface is formed by many intergrown grains, spheres; characteristic of oolitic aggregates;

earthy - has a rough matte surface (kaolinite);

concave - has the appearance of a concave, concentrically wavy surface (flint);

splinter - the surface is formed by equally oriented needles (hornblende);

stepped - a surface in the form of steps dividing cleavage planes (feldspars, halite, galena);

uneven - a chaotically broken shiny surface of solid minerals devoid of cleavage (nepheline).

Colour minerals is an important diagnostic feature. Minerals have different colors: white, gray, yellow, red, green, blue, black. They can also be colorless. In practice, the color of minerals is determined by eye by comparison with well-known objects: milky white, apple green, straw yellow, etc. The color of minerals depends on their chemical composition and impurities. Some minerals (labrador) change color depending on the lighting conditions, acquiring a beautiful rainbow color. This property of minerals is called iridescence ... Sometimes, in addition to the main color, a thin surface layer of the mineral has an additional color, while its surface shimmers with a blue, red, pinkish-violet color (chalcopyrite, bornite). This phenomenon is called temper ... The tint is due to the interference of light in thin films formed on the surface of the mineral as a result of various reactions. There is also a significant amount of minerals that do not have a permanent color (quartz, halite, nepheline, etc.), and, accordingly, color for them cannot be a diagnostic sign. In such cases, as well as when other external features of different minerals coincide, it is useful to define a feature.

Trait Is the color of the mineral powder. Many minerals in a crushed or powdery state have a different color than in a lump. So, pyrite in a piece is straw-yellow in color, and in powder it is almost black. To determine the trait, a piece of mineral is drawn several times over an unglazed porcelain plate (provided that the hardness of the mineral is less than the hardness of porcelain). If the mineral is too hard, then a powder is obtained by abrading it with an even harder mineral. As a rule, if with the help of porcelain it is not possible to determine the color of the powder, then they write that the mineral has no trait.

Other properties combine other, often strictly individual characteristics of minerals. However, other properties often play a critical role in diagnostics, especially in related minerals (halite and sylvite). Specific the weight depends on the chemical composition and structure of the mineral. All minerals can be divided by specific gravity into three groups: lungs with a specific gravity of less than 2.5 (amber, gypsum, halite); medium - with a specific gravity of 2.5-5 (apatite, corundum, sphalerite); heavy - with a specific gravity of more than 5 (cinnabar, galena, gold). The specific gravity of minerals in the field is determined approximately - by weighing on the hand (only one mineral should be present in the sample). Transparency - release minerals opaque, i.e. not transmitting light rays even in very thin plates (native metals, many sulfides, iron oxides); translucent only in a thin plate (along a thin edge, like feldspars, flint, many carbonates); translucent that transmit light like frosted glass (gypsum, chalcedony); transparent that transmit light like ordinary glass (rock crystal, Icelandic spar). Some minerals are characterized by special, only inherent properties. For example, the ability of carbonate minerals to enter into reaction with hydrochloric acid ("boil"). A number of minerals are characterized by magnetism (magnetite, pyrrhotite) - they deflect the magnetic needle. For diagnostics in the field, it matters solubility minerals in water or acids and alkalis. Halite and sylvin dissolve easily in water. The same minerals have taste - salty in halite, bitter-salty in sylvin. Natural alum has a sour, astringent taste. Sometimes minerals have smell ... Thus, arsenopyrite and native arsenic smell of garlic on impact; pyrite, marcasite - smell of sulfur dioxide; phosphorite on friction - the smell of burnt bone. Some minerals oily to the touch (talc), others - easy dirty hands (graphite, pyrolusite). Double refraction possesses Icelandic spar. Fluorescence characteristic of fluorite. Hygroscopicity possess kaolin, sylvin, carnallite. Radioactivity minerals containing uranium and thorium differ.

To determine minerals, they use determinants and tables, which are compiled on the basis of a study of their physical properties. Having determined the hardness, it is necessary to establish the brilliance of the mineral, then the color of the line, cleavage and other external signs. Further, taking into account the hardness and gloss of the mineral, we find in the table below the description that most closely matches all the physical properties of the sample under study. Minerals in the table are ranked in order of increasing hardness (soft, medium hard, hard), in each of the groups luster is taken into account (metallic, non-metallic).

To diagnose (determine) minerals, they are separated into special groups, for example, from the point of view of their use as raw materials for enterprises, material for facing, various crafts, for jewelry, etc. In this case, classification principles are most often used, which are based on regularities the structure of minerals is the chemical composition, features of the structure, texture, etc., which are reflected in external signs. Outward signs are landmarks that enable the lover not to get lost in the world of stones.

There are many tools and analytical methods for examining both individual minerals and rocks.

For an amateur, the first and, perhaps, the only method of determination is a visual inspection. Examining, it is necessary to identify and formulate the properties of an unknown mineral, its brilliance, color, shades, hardness, shape, ability to crack, transparency and other features.

Most minerals in nature are found in a crystalline state.

Usually they have only their inherent crystal shape. Halite cubes, rutile needles, calcite rhombohedrons, etc. Minerals, as is already known, can also be in a non-crystalline, amorphous form, for example, opal, chalcedony, jet.

Pronounced, individual crystals are rarely found. Usually they find their clusters - aggregates.

Aggregates of crystals are granular, dense, needle-like, prismatic. For rock crystal, druses are characteristic - aggregates of crystals, attached as in a brush, with one end to the base.

Native copper and manganese oxides in various rocks and minerals can be found in the form of dendrites - branched, tree-like aggregates. Some aggregates, such as amethyst - purple quartz - are often found in the form of nodules or geodes - cavities or voids filled with mineral matter.

In geodes, crystals grow from the outskirts to the center, in nodules - from the center to the periphery.

Minerals can also be found in the form of film deposits, oolites, which look like sticky balls. The form in which this or that mineral occurs is one of its distinctive features. Some of the physical properties of minerals, such as density or magnetism, are stable.

Other properties for the same mineral can vary depending on the surface quality, such as gloss, or masked by a microcrystalline structure, such as cleavage. The third properties, for example, color, are very characteristic for some minerals, while in others they change from one sample to another. Therefore, for a correct visual diagnosis, it is necessary not only to know the external signs of minerals, but also to understand the role of each sign in the diagnosis.

The determination technique is available to everyone. Diagnostic searches and self-identification experiments are fun and are a good way to study minerals.

At first, it is enough to be able to recognize the external signs of minerals, which include the shape, symmetry of crystals, the characteristic appearance of aggregates and individuals, color, hardness, luster, etc.

Gloss is a qualitative characteristic of the reflection of light by the surface of a mineral - an important feature of minerals. There is a metallic luster, when the surface of a mineral shines like a metal (minerals of the group of native elements, as well as most granular compounds and some oxides); approaching metal - metalloid, as, for example, in graphite; glass (quartz, calcite); pearlescent - in talc and some varieties of mica; oily, when the surface of the mineral is like oily (native sulfur or quartz); silk - for minerals with a fibrous structure - asbestos, fibrous gypsum, as well as glass and diamond luster.

More than half of the minerals on the edges and fractures of crystals have a glassy luster: calcite, topaz, amphiboles, pyroxenes, and others. Examples of minerals with a diamond luster are cinnabar, sulfur, cassiterite, etc.

When differentiating the nature of the gloss, it must be remembered that the degrees of gloss are conditionally delimited, in fact there are no sharp transitions between them. The block structure of the crystal, microfracturing, inclusions, erosion and weathering of the surface, films and flakes of foreign minerals - all this reduces the gloss and sometimes makes this feature unreliable. In fine-crystalline aggregates, the eye perceives the general picture, and not individual individuals, therefore, the brilliance of the mineral may be different than in large crystals. So, well-formed gypsum crystals have a glass luster, and the parallel-fibrous variety gypsaselenite is silky. When subjected to shock or pressure, the gypsum crystals acquire a pearlescent sheen.

Mineral varieties can also differ in luster. So, andradite, like other garnets, has a glass luster, but in demantoid it approaches diamond. To assess the gloss, a clean and dry surface of the stone is considered.

The color and coloration of minerals is very diverse. They depend on various reasons for the chemical composition, inclusions of other substances, structural features and are the most important diagnostic feature. However, it often happens that the color of the same species can vary widely. Some minerals change color when crushed, worn out. For example, pyrite in individual crystals is brass-yellow, and in powder it is black. By this property, it is easily recognizable.

The color can be inherent in the substance of the mineral itself, in particular, due to the presence in the composition of the mineral of the so-called chromophores - the chemical elements of chromium, manganese, iron, cobalt, nickel, copper, titanium. This color is called idiochromatic. Often the color is due to some defects in crystal structures, "iridescence" - inhomogeneous refraction and reflection of light due to the lamellar inhomogeneity of the crystal.

Many minerals are named for their color. For example, albite - "white", orpiment - "gold color", hematite - "bloody", celestine - "sky blue", citrine - "yellow", etc. From the same Persian root meaning "blue ", The names of three blue minerals - azurite, lapis lazuli, lazulite occurred. However, for the most part, the names of flowers exist in Greek and Latin.

The permanent color of the mineral is of paramount importance. Sulfur is always yellow, azurite is blue, malachite is green, rhodochrosite is pink, etc. And at the same time, the color can change. This can happen due to the presence of impurities.

For example, calcite can be colored by impurities in blue, lilac, yellow and other colors. Ruby red and pyrope, eurid green and uvarovite owe their color to chromium impurities. Chromium-containing alexandrite and kemmererite are green in sunlight, and violet under electric light. The wide distribution of iron and chromium in the earth's crust explains the reason for the distribution of brown, red and green shades in minerals. In contrast, few blue minerals are found.

The color of a mineral always means primary colors, idiochromatic, inhomogeneous colors can serve as additional diagnostic signs.

The color of the mineral must be observed on a fresh, clean surface of a facet or fracture, when it is not masked by deposits, oxides, weathering, films.

Tint is a specific light play or other additional effect, and sometimes an iridescent color of the surface, inherent in minerals with a metallic sheen. Some chalcedony have a bright blue color due to the scattering of light in the microporous surface layer. When moistened, the color disappears, and when it dries, it reappears.

Trait color is essential in identifying minerals. The line left on the matte, unglazed surface of porcelain consists of a fine powder of the mineral. The color of the trait is not as saturated, bright and rich in shades as the color of crystals, but this is a more permanent feature that is used when determining opaque densely colored minerals. Light colored minerals tend to give the same white streak. By the color of the crystals and the color of the trait, it is sometimes possible to establish the presence of chemical impurities and the place of the mineral in the isomorphic series. The color and trait of dark minerals must be viewed in bright light.

The ability of one mineral to scratch the surface of another depends on its hardness. Hardness characterizes the resistance of a mineral to destructive mechanical stress on its surface. This resistance is due to the structure of the crystal and the strength of the chemical bonds. Hardness decreases with defects and inhomogeneous structure. Minerals are conventionally divided according to the scale of the Austrian mineralogist Friedrich Moos into ten groups, arranged in ascending order of hardness.

The ordinal number or coefficient is determined as follows: if any mineral scratches, for example calcite, having a hardness of 3, then its hardness is indicated by a coefficient of 3.5 (or 3-4).

Mohs hardness scale

1. Talc 6. Orthoclase

2. Gypsum 7. Quartz

3. Calcite 8. Topaz

4. Fluorite 9. Corundum

5. Apatite 10. Diamond

Of all the known minerals, diamond is the hardest, and corundum is the only one with a hardness of 9.

In the field, the objects at hand are usually used to determine the hardness of minerals. So, the hardness of the lead of a soft pencil is about 1; nail - 2–2.5; copper coins - 3-4; an iron nail - 4–4.5; a piece of glass - 5; steel knife blades - 6; file - 7.

According to the degree of transparency, transparent minerals are distinguished - rock crystal, diamond and opaque - graphite.

Cleavage is the ability of a mineral to split in certain directions. Cleavage is very perfect, perfect and imperfect. Quartz has no cleavage - this is also a diagnostic sign.

Minerals with well-defined cleavage are called spars - from the old German word meaning "to split". For example, fluorspar - fluorite, Icelandic spar - calcite, etc.

Cleavage of transparent and translucent crystals is often detected by the presence of cleavage cracks, for example in calcite. Cutters take this property into account when grinding and cutting stones.

The fracture of the mineral is also an important characteristic. In the presence of cleavage, the fracture in the direction of cleavage will turn out to be smooth, in the absence of cleavage - conchial, similar to the inner surface of the shell, such as in opals, chalcedony, volcanic glass. A crusty fracture is also characteristic of calcite, quartz, topaz, and many other minerals. It allows you to get sharp edges from obsidian and flints, which was extremely important for the manufacture of knives, scrapers and other stone tools in ancient times.

The fracture can be splinter, resembling a transverse fracture in wood. Such a break often occurs in minerals of a fibrous structure - asbestos, fibrous gypsum, tourmaline.

The fracture can be hooked, such as in native copper and silver, and granular, like in apatite, etc.

The main feature of iron-containing minerals is magnetic.

It is characteristic of a few minerals - pyrrhotite, magnetite, platinum, native iron. Magnetic minerals are attracted by magnets and in large masses deflect the compass needle. A small piece of mineral, 2–4 mm, is tested with a magnet.

Flavor is important when determining salts. In halite (table salt) it is salty, in sylvite (potassium salt - bitter-salty).

Smell is a hallmark of some minerals. Pyrite, for example, smells like sulfur, and arsenic minerals smell like garlic.

In order to learn how to identify minerals, you need to spend more time getting to know them, trying to remember them, noting external signs, characteristic forms, communities with other minerals, and the environment.

Experience and practical skills will help to recognize some mineral species in familiar samples, then the ability to distinguish an increasing number of them and in a more diverse form will come.

It is necessary to take it as a rule to determine a mineral by a set of features, including the form of separation, minerals-satellites, the type of deposit where it was found. This requires a certain amount of mineralogical literacy, which is very important for amateurs and gatherers of stones. Mineralogists and experienced collectors recommend that you master the tried and tested methods of good mineral determinants and stick to them.

A set of characteristic features makes it possible to recognize minerals not only when they are presented as individual minerals, but also in the composition of rocks.

So, quartz and mica are recognized in granite, and calcite in marble, etc.

Rocks are composed of various minerals and are part of the shells of the earth's crust. Why are minerals formed?

Describers of stones - petrographers divide them, rocks, into three large groups, depending on their origin.

The first group includes igneous rocks. They were born in the lowest parts of the earth's crust and the top of the mantle. The mantle is the shell of the Earth located between the crust and core of the planet. The processes of radioactive decay of elements, the energy of movement and redistribution of matter, heat fluxes, thermonuclear and chemical reactions, and other, not yet known forces, melt rocks that take place there. This is how primary magma centers are formed in the solid Earth.

In the depths of the Earth, there are huge pressures and magma is there in a plate-like, close to solid state, but as soon as the pressure decreases as a result of the formation of various cracks, splits, uplifts of land plots, etc., the substance of the hot substance turns into a liquid state - the magma itself , the ancestor of igneous rocks.

Igneous rocks rise along cracks and channels closer to the earth's surface. If magma finds a way out and pours out onto the surface of the earth in the form of lava, for example, during a volcanic eruption, volcanic (erupted) rocks are formed from it, which are one of the varieties of volcanic. If the magma does not reach the surface, gets stuck along the road and does not erupt, then when the temperature drops, the so-called intrusive (intrusive) rocks crystallize. Intrusive rocks are another type of magma.

The second group includes sedimentary rocks. Their origin is associated with the processes of deposition in the seas, lakes, oceans brought by rivers, winds, ice and other means of various materials.

This material falls to the bottom in the form of particles - this is how clays, sands, etc. are formed, or crystallizes from solutions (salt, travertine, dolomite).

Sedimentary rocks are also formed from organisms whose skeletons are built on lime or silica. Particles of corals and shells accumulate at the bottom of reservoirs and this sediment, compacted and displacing water, turns into rock. There are many varieties of sedimentary rocks.

The third group includes transformed breeds. They arose under the influence of high temperatures and pressures in the depths of the Earth - these are metamorphic rocks - marble, crystalline schists, etc. or by replacing some minerals with others at relatively normal temperatures and pressures - these are metasomatic rocks. Most granites and others are referred to metasomatic rocks.

Regardless of their origin, all rocks are subdivided, depending on their silica content, into acidic, medium, basic and ultrabasic. As applied to igneous rocks, this classification is associated with the depth of the magma chamber - the amount of silica decreases from top to bottom from the Earth's surface to the mantle. At a depth of 60 - 100 km silica contains less than 45 percent and magma has a basic, and possibly ultrabasic composition. In this composition, there are primary foci of such rocks as peridotites, basalts, etc. They, as a rule, are enriched in oxides of calcium, iron, magnesium.

Closer to the surface, acidic and intermediate melts can arise, which give diorites, igneous granites and other rocks in which the silica content is increased.

There are very few volcanic rocks that arose from silicic magmas - about 13 percent of the entire area of ​​distribution of igneous and metasomatic rocks.

The share of granites is approximately the same. However, in relation to granites, according to some researchers, there is a kind of secret. Granite consists of the most common minerals - quartz, feldspar, mica - and is familiar to many. It seems that there is no secret, and at the same time it exists. It consists in the fact that until now it has not been precisely established where and how granites and their "relatives" - granitodiorites, granite gates, etc. were born.

This story is long and began in the second half of the XUIII century, when a scientific war broke out between the "neptunists" who explained the appearance of all rocks by their precipitation from a "chaotic fluid" and "plutonists", who argued that all rocks are of fiery origin. The struggle between scientists lasted for many years. It should be noted that the origin of the stone to this day causes controversy, though not so hot and stubborn. In the XX century they subsided, as it became clear to many that there were sedimentary rocks - sands, clays, limestones, and there are igneous rocks - basalts, gabbros, granites. The former were formed in various water bodies by precipitation, the latter - from fiery liquid melts of a complex, predominantly silicate composition, saturated with volatile compounds - magma, melt their way in rocks, rise along cracks and freeze in the upper parts of the crust or pour out onto the surface in the form of volcanic lava.

According to modern concepts, the deep substance of the Earth is gradually degassed, that is, it loses volatile components. Some of them, together with magma, are transported to the Earth's surface and released into the atmosphere when the pressure drops. The other part forms superheated gas-liquid solutions at depth, which mainly consist of water and carbon dioxide. These solutions also rise to the surface, having a strong effect on the minerals of the rocks along the way.

But geophysicists, with the help of special instruments, proved the absence of a continuous molten shell on the Earth, there are only individual foci of magma. These studies created a crack in the theory of the magnetogenic origin of granites, because there are quite a lot of granites and they fill huge spaces, and the centers of melt are, in fact, points. A strip of granites stretches from Lake Baikal to the Sea of ​​Okhotsk for many kilometers. It cannot be assumed that in one or two areas the earth threw out such a huge mass of granite lava. Such a huge wedge would split the planet. Then they began to collect facts that speak in favor of the origin of most of the granites in the very place where they are found today.

However, the simplest classification of rocks into sedimentary and igneous was soon disturbed. The fact is that parts of the earth's crust, for various reasons, can sag and descend along cracks in separate blocks, falling together with the rocks composing them in the region of high temperatures and pressures. The rocks there change and become metamorphic - transformed. Metamorphic rocks of granite composition are practically indistinguishable from igneous ones. It is so difficult to distinguish them that they have come up with special names for medium, as it were, intermediate rocks, for example, granite gneiss.

If it is gneiss - metaphorical, and granite - igneous rock, then how to represent the origin of gneisses? The problem of the origin of granite was not solved, and then the hypothesis of the metasomatic genesis of granites arose.

Metasomatism is the process of replacing one mineral with another, the struggle of crystals for space and solutions. In the struggle between minerals of different composition, the front line sometimes stretches for hundreds of kilometers. As a rule, the winners are feldspar and quartz in the union, which supplant other minerals. The replacement processes go on until a chemical equilibrium is established, and they fade out most often at the moment of granite formation.

So far, it is recognized that granites and other rocks that have recently been classified as igneous can arise in different ways, but most often through metasomatism.

Be that as it may, granite of different shades. from almost black to pink, it is the most natural stone, like many other colored stones that adorn our lives.

There are minerals that can occur in a very wide range of conditions and are ubiquitous. These minerals include, for example, pyrite and quartz. Most minerals are most commonly found in certain types of deposits. Special, exceptional conditions of formation determine the rarity of such minerals as diamond. The number of mineral species generally increases with decreasing temperature and pressure.

All geological processes occurring on Earth, from volcanic eruptions to the imperceptible evaporation of water from seas and lakes, is accompanied by a redistribution of matter and energy. Various solid, liquid and gaseous substances are destroyed and new ones appear instead. Here and there, there is a renewal of the mineral composition of the earth's crust, such a renewal makes it possible for minerals to form.

COLLECTION OF MINERALS

It is best to gain experience in collecting minerals in a mineralogical circle, in specially organized hikes. In the field, it is possible to conduct observations and it often happens that stone lovers discover the location of one or another mineral.

You can collect stones at any time of the year. Even in winter, where a trench or foundation pit is being dug, you can find something interesting. Interesting stones are also found on the roads leading to the construction site.

Still, the best time of the year to collect rocks is early spring when the snow has just melted. At this time, rare and interesting stones may lie right on the ground washed by spring waters.

Starting the search, you need to establish which part of the study area is worth examining in detail. Here it is important to know which minerals can accompany each other and which combinations you will not find in nature.

When inspecting, for example, ore dumps, it is advisable to invite a companion. In order not to disturb the family, you need to tell your family where you will be and when you will return. And in order to comply with safety regulations, and in order to protect yourself from injuries, bruises, etc., you need to know that the situation of a mining enterprise itself can be sources of hazards if the work is carried out in a mine environment, negligence in relation to mining equipment and improper handling with your own instrument.

Blocks located at a height as a result of landslides, precipitation, shattering of crushed rock, sooner or later roll down, therefore they are under the "peak", that is, under the overhanging block it is impossible. Even in the absence of a visible danger, caution is necessary, because individual stones may roll and even collapse due to insignificant shifts caused by rock disassembly, hammer and sledgehammer blows, etc. You need to work in a protective helmet, carefully observing the condition of the overlying parts of the wall. Hearing the rustle accompanying the rock shedding, you must immediately move to a safe distance. Moving along the slopes, it is necessary to try the reliability of fixing the blocks and observe the rule of support on three points - two legs and a hand or a hammer.

Due to the reduced strength of some rocks, climbing techniques cannot be used in active and abandoned quarries. Only in exceptional cases, after carefully examining the slope and dropping unreliable boulders, you can use ropes and pitons on a slope of little steepness. Here, the following conditions are required: to be alone, reliable insurance, the presence of mountaineering training.

It is extremely dangerous to descend into dips and collapses, enter areas marked by warning signs or separated by fences, approach the edge of a ledge prone to landslides, go over a landslide crack, or is on the slope of a dump or at its base during unloading of a dump vehicle.

You can start work only after you are sure that the breed will not be dumped into it. It is possible to be in the quarry only during daylight hours.

The blasting schedule must be closely monitored.

At the entrance to the quarry, you need to behave so as not to interfere with the work of the equipment: do not leave your belongings and do not stand in the path of traffic, do not stay within the radius of movement of a working excavator, do not sit in the body of a dump truck, do not approach vehicles carrying explosives.

Do not work near electrical devices with high voltage signs.

Your tool must be inspected regularly, detecting malfunctions in a timely manner. Hammers and sledgehammers must be firmly attached to the handles.

A loose instrument can cause not only severe injury, but also damage to specimens. When working with a sledgehammer, those present should be on the sidelines, since it cannot be completely excluded from sliding off the handle or slipping out of the hands. If a crack appears on the firing pin, the tool is no longer used. If a crack appears on the handle, you can only work with gloves.

When working with a hammer or sledgehammer, you need to beware of bruises and wounds from fragments of stone and steel. You need to work in clothes and preferably in goggles, closing your eyes on impact.

Disassembly of cavities with crystals of quartz and other minerals that form sharp fragments must be carried out with gloves.

The water in the quarry must not be used for drinking and cooking.

The rock, which contains efflorescence of vitriol (pisanite, chalcanite, etc.) and other water-soluble minerals, should not be cut with a hammer or sledgehammer, as this raises dust, irritating the respiratory tract and causing a severe cough.

By observing these basic safety rules, you can save yourself from unwanted complications while looking for colored stones. It is best to look for them in a slightly drizzling rain, because wet stones acquire a richer color.

But interesting stones can also be found when digging a vegetable garden. Even at first glance, an unremarkable stone should not be thrown away. You need to put them in one place, and then consider. It takes some time to see the beauty in the stone. The stones hide it under a white or gray crust, which is called a "shirt". Colored stones dressed in such "shirts" are called tonsils or nodules. Sometimes you can't tell them right away from pebbles, marl or dolomite, limestone pebbles. However, looking closely, you can replace some of the features of the shape, color, texture of shirts. These features allow experienced hobbyists to determine what lies beneath them. For example, nodules of agate and flint stand out among other stones in a more complex, sometimes even bizarre shape. You can find a completely nondescript stone that looks like an old wrinkled potato, but when you cut and polish it, a surprisingly clear and clean pattern of agate will open. Each stone is beautiful in its own way, each, like music, evokes its own mood. Many cannot resist the temptation to collect colored stones - beautiful, festive, elegant, bringing joy.

Well, in those cases when the nodules are unremarkable, intuition will help out.

However, as a rule, one cannot count on quick success in diagnostics.

Success comes through years of hard, painstaking research.

Colored stones can also be collected in open pits, operating and spent, dumps, in old mines, ravines, river beds and river banks, in natural outcrops of rocks, etc. In such a persistent search, one of the geologists, who lived in a small Australian town, managed to get opal weighing about three kilograms is the largest gemstone in the world. This happened in 1956, when the Olympic Games were held in Australia. In their honor, the opal was named "Olim Piskiy". The deposit turned out to be the largest in Australia and accounts for more than half of the world's opal production.

While searching, you can't waste time in vain, so you need to prepare for them thoroughly at home. What is this preparation?

First, you need to collect more information about the area where the prospecting will be conducted. Secondly, think over the organization of work, because the daylight hours are short.

Third, prepare tools, equipment, etc.

From the tool they take with them a geological hammer, a small sledgehammer, chisels, a curved scraper, a ripper, a paddle, various wedges, a claw - a crowbar with curved sharp ends and another tool, depending on the work ahead.

Some tools that are difficult to buy at the store can be made by yourself. Only they need to be made, of course, with high quality, because both work productivity and reliability depend on their quality.

A tool that has been in operation must be inspected and, if necessary, repaired.

Hammers with cracks and chips cannot be taken. Loose handles are strengthened by replacing a transverse wedge in them or hammering in an additional one. Just in case, it is recommended to take a couple of oak or beech wedges with you, and if the work is long, then a spare handle will not hurt.

Dull chisels need to be sharpened, bent to straighten. That being said, it is worth knowing that even good hammers, sledge hammers and chisels rarely last more than three field seasons.

The work will need a stiff brush for cleaning samples and cleaning clothes, as well as a needle, strong threads, nylon line, twine, strong rope, insulating or adhesive tape, gloves. They usually wear tarpaulin boots or other sturdy shoes on their feet.

In addition to the above, two backpacks are required. One for stones, one for things. Backpack straps should be wide and strong.

What is the technique for working with a geological tool?

Before entering the field for the first time, it is useful to practice the ability to split various stones. At the same time, granites, limestones, basalts, flints and other rocks behave differently.

Some are easy to trim, others are knitted and difficult to process, others are slate, etc. It is important to skillfully use these properties. In some cases, a strong blow can destroy the stone, and sometimes you need to hit exactly hard, sharply and accurately. Some stones can be chipped lightly with a chisel.

A small stone can be broken with a hammer, placing it on the palm on which the mitten is worn, or on another stone, or on the head of the sledgehammer, holding it with the hand or the toe of the boot. The blow is applied in the middle of the striker. Sharp strikes of the striker cut the edge of an angular stone. With the beak of a hammer, they knock down thin edges, hammer, hook, drag, turn over stones. With a beak, you can widen a crack in a stone, acting like a lever or a wedge, lightly tapping the hammer with a sledgehammer.

Large pieces of rock - lumps are broken with a sledgehammer. At first, strikes are applied with the middle or edge of the striker on the protrusions of its lower part. If there are no protrusions, strong blows are applied. Cracks appear from them, from which the cutting of the lump begins.

If you need to cut or remove a layer of turf, then do it with a paddle. With its help, the rock is exposed under a layer of soil or rubble. It is convenient for them to dig up crushed stone, loose earth, debris or to clear the place of work - "face". First, the toe of the stroke is used to clean the angle between the wall and the bottom, then the debris is raked up with the wide side and pulled out of the face.

Cracks are wedged with a chisel. They hold it with their left hand, and carefully hammer it into the crack with a hammer or sledgehammer. When the chisel enters and holds steady, it will be hammered harder. If the crack is wide, pieces of a round metal bar are placed under the chisel. With a chisel, they knock out grooves in the rock, separate crystals and small intergrowths. The narrower the working edge of the chisel, the better it will work, but also the greater the risk of breaking it.

A straight crowbar can be used as a long chisel. The claw is used as a lever when moving blocks, turning them inside out, or when pushing layers apart.

Sometimes the use of a claw can help retrieve fragile specimens.

It often happens that in order to obtain a sample, it is enough to open a small circular cavity - a geode. Such cavities are taken entirely, if possible, separating excess rock and postponing more complex work until returning home.

The geode is separated with a claw, after knocking out the sections of the rock that interfere with its extraction. Fragile and thin-walled geodes cannot be removed this way.

Then the surrounding rock is disassembled along the cracks until the geode is completely free. If there are no cracks, then an artificial crack is created around the geode in a closed circle. To do this, carefully drive in several round chisels and, in turn, hit them with a hammer until a crack appears in the desired direction.

As the crack spreads, the last chisels are removed and driven in front.

In larger geodes, this can extract wall sections and loose crystals that are in its interior space. If the cavity is large enough to climb inside, it works like an outcrop wall.

The future sample and its base are cleaned of debris, dirt and carefully examined. Most often, the desired fragment can be separated with the help of a claw. If the fragment is held firmly, then cracks are wedged from one or both sides with a chisel and a hammer, or a sufficiently deep groove is made along the contour, and then the sample is chipped off with a chisel. In this case, so that the chisel does not fall and to reduce vibration, it is held by a partner. If the sound of the impact becomes more and more muffled, then the crack is widening and you need to work more carefully. It is not often possible to find a cavity with good crystals.

If the geode is small and cannot be penetrated, it is opened with a few careful blows to produce a crack. Here you need to be careful not to damage the crystals inside. The mouth of the geode must be opened so that the crushed stone, earth, etc. filling the cavity can be carefully removed with a stick or wire hook.

The selected land and rubble are carefully examined. They may contain good crystals and parts of the walls that have fallen inside.

The "mountain skin" on a part of the samples can be left as is. It can be used to judge the conditions of mineral formation, and besides, both "mountain skin" and "mountain cork" give the sample a special appeal.

Then they begin to process the walls of the cavity. First, they release the bottom from damage that collapsed walls can cause. On the vacant space, put some kind of litter and, starting from the bottom, disassemble the side walls, and then the arch. As a result of rock alteration, an empty or soft-filled gap is sometimes formed around the cavity. It makes it possible to work with a claw. After separation of the wall parts closest to the mouth, further disassembly of the cavity is easier.

Dump disassembly. Before you start disassembling the blade, you need to find out its features, what and in what place can be found in it.

The dump consists of rock debris recovered during surface penetration to the ore body. The crushed rock is transported by dump trucks or trolleys to the top of the dump and dumped onto its slopes. In this case, the dump material is deposited in the same sequence in which it is removed from the mine. Interesting material can often be found in one layer of the dump, as it is taken from one place. The productive layer has the shape of a cone and is located in an arc in the horizontal section, and in a straight line along the slope in the vertical section, forming a kind of blanket.

The largest blocks, when dropped, roll down, stopping at the base of the dump and on its sides. Smaller debris accumulates above and on the flanks, while small debris lingers near the top. Cavities with crystals should be looked for, most likely in lumps in the lower part of the dump. The material from which ore can be knocked out is in the middle and at the edges, and individual crystals are at the ridge and below the top.

It is sometimes difficult to understand how the dumps are located. Careful tracking of the transport route will help to understand. If a sample of the material was found in the productive layers, then it is possible that there are others in the same layer.

It is best to work on the dump after rain, when the stone is washed and clearly visible, but when moving you need to be careful - it is slippery. Disassembly starts from the flanks. To find the productive layer, they dig a ditch from the bottom up.

The wreckage is sorted out with a stroke, hammer beak or hands, quickly inspected and moved on. Going out to the desired layer, dig it to the sides. Fine material can be washed. It is placed in a wicker bag or wire basket, immersed in water, then sprinkled in a thin layer and examined.

If excavations have already been carried out on the dump, you need to dig a deep hole - a pit.

The pit will provide an opportunity to view the lower parts of the dump.

Working on debris and loose sediments is similar to parsing a dump. The debris is carefully removed to expose the deposits underneath. First, vertical grooves are made across the talus with the toe of the stroke. You need to dig to the root base - "raft". If an interesting place is found, it is exposed along the entire required site. They start from the bottom, gradually move upward, from time to time discarding the accumulated material with a stroke. In the same way, from bottom to top - loose layers are taken apart, exposed in the wall. If necessary, make a hole or ditch of the required depth.

In order to extract an interesting sample from a large block, you need to cut the block and gradually remove everything unnecessary until the desired fragment remains.

However, this fragment is the most fragile part of the block and may be the first to suffer. To prevent this from happening, the rest of the lump, in which the fragment is located, must be more massive than the detachable part. If there is no suitable crack along which it would be possible to wedge and break the lump, it is chipped in several steps, starting from the side opposite to that where the sample is located. In this operation, it is necessary to strike correctly and strongly, which will not only separate most of the block, but create the prerequisites for the next stage, leaving a new protrusion on the block. Approaching the sample, the instrument is changed to a lighter one.

It is rather difficult to open agates, flints, nodules intended for cutting and polishing. The main thing here is to avoid cracks that will spoil the appearance of the polished surface. If it is not possible to beat off the edge of the stone without cracking, then it is better to take it whole. True, it may happen that after cutting it, it turns out to be uninteresting.

Found samples should be washed and examined. Discard uninteresting samples, and separate high-quality samples from excess breed and pack them.

The best samples are grouped according to mineral species, varieties, places of discovery, morphological characteristics and are carefully studied under good lighting under a magnifying glass.

Damaged or broken samples are repaired with glue of the "Moment" type, PVA, nitro glue, without delay, because over time, the edges of the stone fragments crumble and the seam will not turn out invisible.

Minerals are determined by the following properties: the color of the mineral and the color of its features on a porcelain plate, luster, transparency, hardness, cleavage, separateness, fracture, magnetism and specific gravity.

Mineral color... The color of minerals is extremely diverse and depends on the absorption of some rays of the spectrum and the reflection of unabsorbed rays. Some minerals are characterized by a constant color, so magnetite is always black, and malachite is green. Other minerals have different colors, for example, quartz is white, yellowish, smoky, pink, purple, black, sometimes colorless and transparent. Feldspar in granite is pink, sometimes meat-red or gray, etc. The colors of minerals are determined in practice by comparing them with well-known, more or less firmly established colors, for example, they say: golden yellow, pewter white, lemon yellow, indigo blue, bottle green, straw yellow, etc. Some transparent minerals have the property of changing color in the same crystal, depending on the angle at which they are viewed or depending on the nature of the lighting.

Line color... The true color of the minerals is well defined in the powder of the crushed sample. To obtain the powder and determine its color, draw an acute angle of the mineral on a white uncoated porcelain plate or, even easier, on a fresh fractured porcelain dish. The color of the trait does not always match the color of the mineral. So, in multi-colored fluorites, the color of the features of the samples of almost black, red and colorless fluorite turns out to be equally colorless. Quartz does not give a trait, magnetite gives a black trait, multi-colored feldspars - white or colorless, like dark green olivine. The color of the mineral should be observed on fresh surfaces, since the tested mineral can be covered with deposits of other minerals and, due to weathering, can change the color on the surface. In addition, minerals can be covered with "tarnishing", that is, an iridescent film that changes their true color, as we see in a Labrador retriever.

Shine. Most minerals have the ability to reflect light on their surfaces, which explains their brilliance, which serves as an important diagnostic feature for all minerals. Shine must be studied on fresh breaks, as well as color. There are the following types of mineral shine:

shine metallic- strong, reminiscent of the luster of a polished metal surface. Minerals with a metallic sheen are usually opaque and heavier than others. These include: gold, pyrite (pyrite), chalcopyrite (copper pyrite), arsenopyrite (arsenic pyrite), galena (lead luster), magnetite (magnetic iron ore), pyrolusite, molybdenite, pyrrhotite, bismuth, antimonite (antimony) dr.

The metallic or semi-metallic luster resembles the shine of metals that has faded from time to time. It is typical for graphite, anthracite, rutile, cuprite, hematite, etc.

Non-metallic luster.Diamond glitter- due to the reflection of light from the inner surfaces of the mineral and is characteristic of transparent or translucent minerals with a high refractive index. Example: diamond, sphalerite (zinc blende), cinnabar crystals, cerussite (white lead ore), etc.... The latter sometimes has a glassy luster, depending on the angle of incidence of the light.

Glass luster resembles the luster of glass, but is less pronounced than that of minerals with a diamond luster. It is possessed by many transparent minerals. Example: quartz on the edges of rock crystal, calcite, gypsum, olivine (the latter also has a greasy luster), orthoclase, fluorite, garnet, corundum, etc. ... Bold shine resembles a surface greased or oiled. It is typical for soft minerals. Example: talc, serpentine, eleolite, nepheline... The latter has a greasy luster in a fracture, and on the planes of crystals it is glassy, ​​like quartz, and sulfur, with a greasy luster in a fracture, has a diamond luster on the edges. Pearlescent shine with a dull iridescent iridescent color, similar to the luster of mother-of-pearl, is observed on the cleavage planes and is caused by the reflection of light from the cleavage planes of the mineral. Example: mica, calcite, labrador. Silky shine- shimmery - due to the fine-fibrous structure of the mineral. Example: fibrous gypsum (selenite), asbestos... Malachite has a glassy luster, sometimes up to diamond, in some fibrous varieties the luster is silky. Wax- low oily to matte sheen. Example: chalcedony.

For matte or dull minerals like bauxite, the complete absence of any shine is characteristic. Also devoid of shine: chalk, various ocher, sooty pyrolusite. Kaolinite in a continuous mass - matte, but its individual scales and plates are characterized by a pearlescent sheen.

At first, until the geologist has a “geological eye”, it is difficult for him to catch subtle shades in the color of individual minerals. Different shades of colors, like gloss, are easier to catch by comparing samples. For example, the straw-yellow color of pyrite in the immediate vicinity of copper pyrite contrasts markedly with its brass-yellow color.

Transparency. Transparency - the property of transmitting light - is determined by thin fragments of minerals or in plates. According to the degree of transparency, minerals are divided into the following groups: transparent ( rock crystal, rock salt, gypsum, Icelandic spar, topaz, etc.), translucent ( chalcedony, opal, beryl, sphalerite, cinnabar, etc.), translucent in the mass ( jade, rhodonite, etc.), translucent at the edges ( feldspars, etc..), opaque ( graphite, magnetite, pyrite, etc..). Except for the last category, all minerals are transparent in thin sections, that is, when examined under a microscope in transmitted light, plates with a thickness of about 0.02 mm. Ore minerals are overwhelmingly opaque.

Hardness... Hardness is understood as the degree of resistance of a mineral to scratching, grinding, drilling, pressure, etc. The hardness of minerals is quite varied for different minerals and is more or less constant for the same, moreover, it is easily and quickly determined. To assess the hardness, it is accepted Mohs scale , including a list of ten minerals, of which each subsequent scratches all the previous ones.

For diagnostics (that is, determination) of minerals, they are separated into special groups, for example:

• use as raw material for enterprises,
• material for cladding,
• stones for various crafts,
• stones for jewelry, etc.

Most often they use the principles of classification, which are based on the laws of the structure of minerals - these are chemical composition, features of the structure of the mineral, texture and so on, that is, external signs. External signs are landmarks that enable the lover not to get lost in the world of stones. Knowing how to identify stones is also important for jewelry lovers, so as not to be mistaken and to be able to recognize natural stones.

For an amateur without special equipment, the first and probably the only method of determining a stone is a visual inspection. Examining, it is necessary to identify and formulate the properties of an unknown mineral, its brilliance, color, shades, hardness, shape, ability to crack, transparency and other features.

Crystals and other forms of minerals

Apatite. Apatite is the main raw material for the phosphate fertilizer industry.

Most minerals in nature occur in a crystalline state.

Crystals usually have only their inherent shape. Halite cubes, rutile needles, calcite rhombohedrons, etc. Minerals can be and in non-crystalline, amorphous form eg opal, chalcedony, jet.

Pronounced, individual crystals are rarely found. Usually they find their clusters - aggregates.

Aggregates of crystals are different - granular, dense, needle-like, prismatic... Rock crystal (and not only it) is characterized by druses - aggregates of crystals attached, like in a brush, with one end to the base.

Native copper and manganese oxides in various rocks and minerals can be in the form of dendrites (dendrites) - branched, tree-like aggregates. Some aggregates, such as amethyst - purple quartz - are often found in the form of nodules or geodes - cavities or voids filled with mineral matter.

In geodes crystals grow from the outskirts to the center, and in nodules- from the center to the periphery.

Minerals can occur and in the form of film deposits , oolites, which look like balls stuck together.

The form in which this or that mineral occurs is one of its distinctive features. Therefore, collectors often prefer to collect unprocessed stones, but their natural forms - here the minerals are very individual and very different from each other.

Some of the physical properties of minerals, such as density or magnetism, are stable.

Other properties for the same mineral may vary depending on the quality of the surface (its processing): gloss, or masked by a microcrystalline structure, like cleavage. Third properties, for example, color, are characteristic of some minerals, while others vary greatly from one sample to another. For correct visual diagnostics, it is necessary not only to know the external signs of minerals, but also to understand the role of each sign in diagnostics - sometimes the color is secondary, sometimes it is more important, etc.

At first, it is enough to be able to recognize the external signs of minerals - the shape, symmetry of crystals, the characteristic appearance of aggregates and individuals, color, hardness, luster, etc.

Shine

Gloss is a qualitative characteristic of the reflection of light by the surface of a mineral - an important feature of minerals. Distinguish:

• metallic shine, in which the surface of the mineral shines like a metal (minerals of the group of native elements, as well as most granular compounds and some oxides);
• approaching metal - metalloid, as, for example, in graphite;
• diamond luster - not only diamond has it, but also some other minerals; examples of minerals with diamond luster are cinnabar, sulfur, cassiterite and others;
• glass luster (quartz, calcite, and many other minerals);
• pearlescent - in talc and some varieties of mica;
• oily, when the surface of the mineral is like oily (native sulfur or quartz);
• silk luster - for minerals with a fibrous structure - asbestos, fibrous gypsum, as well as glass and diamond luster.

More than half of the minerals on the edges and breaks of crystals have a glassy luster: calcite, topaz, amphiboles, pyroxenes and others.

The degrees and types of gloss are conditionally delimited, in fact, there are no sharp transitions between them. The block structure of the crystal, microfracturing, inclusions, erosion and weathering of the surface, films, flakes of foreign minerals - all this reduces the gloss and sometimes makes this feature unreliable, it cannot be used as the only one. Moreover, in fine-crystalline aggregates, the eye perceives the general picture, and not individual individuals, therefore, the brilliance of the mineral may be different than in large crystals. Well-formed gypsum crystals have a glassy luster, while the parallel-fibrous variety of gypsum selenite is silky. When subjected to shock or pressure, the gypsum crystals acquire a pearlescent sheen.

Mineral varieties can also differ in luster. So, andradite, like other garnets, has a glass luster, but in demantoid it approaches diamond.

To assess the gloss, a clean and dry surface of the stone is considered.

Mineral color

The color, coloration of minerals is very, very diverse. They depend on the chemical composition, inclusions of other substances, structural features of the mineral and are the most important diagnostic feature. But it so happens (and quite often) that the color of the same species can vary over a very wide range. Some minerals change color when crushed, worn out. For example, pyrite in individual crystals is brass-yellow, and in powder it is black. By this property, it is easily recognizable.

The color can be inherent in the substance of the mineral itself, that is, due to the presence in the composition of the mineral of the so-called chromophores - the chemical elements of chromium, manganese, iron, cobalt, nickel, copper, titanium. This color is called idiochromatic.... But the color can also be caused by some defects in crystal structures, "iridescence" - inhomogeneous refraction and reflection of light due to the lamellar inhomogeneity of the crystal.

Many minerals get their name from their characteristic color. For example, albite - white in translation, oripigment - gold color, hematite - bloody, celestine - sky blue, citrine - yellow, etc. From the same Persian root meaning the word "blue", the names of three blue minerals - azurite, lapis lazuli, lazulite... But for the most part color names exist in Greek and Latin.

Celestine.

The constant (unaltered by different conditions) color of the mineral is of paramount importance. Sulfur is always yellow, azurite is always blue, malachite is green, rhodochrosite is pink, etc.

And at the same time, the color of the stone can change. from different conditions This may occur due to the presence of impurities.

For example, calcite can be colored by impurities in blue, lilac, yellow and other colors. Ruby red and pyrope, eurid green and uvarovite owe their color to chromium impurities. Chromium-containing alexandrite and kemmererite are green in sunlight, and violet under electric light.

Celestine.

The wide distribution of iron and chromium in the earth's crust explains the reason for the distribution of brown, red and green shades in minerals. In contrast to this there are comparatively very few blue minerals.

The color of a mineral always means primary colors, idiochromatic, inhomogeneous colors can serve as additional diagnostic signs.

The color of a mineral must be determined on a fresh, clean surface of a facet or fracture, when it is not masked by deposits, oxides, weathering, films.

Tint is a specific light play or other additional effect, and sometimes an iridescent color of the surface, inherent in minerals with a metallic sheen. Some chalcedony have a bright blue color due to the scattering of light in the microporous surface layer. When moistened, the color disappears, and when it dries, it reappears.

Trait color is very important in identifying minerals. The line left on the matte, unglazed surface of porcelain consists of a fine powder of the mineral. The color of the trait is not as saturated, bright and rich in shades as the color of crystals, but it is a more permanent feature that is used when determining opaque densely colored minerals that are difficult to identify.

Light colored minerals usually give the same white streak.

By the color of the crystals and the color of the trait, it is sometimes possible to establish the presence of chemical impurities and the place of the mineral in the isomorphic series. The color and trait of dark minerals must be viewed in bright light.

Mineral hardness

The ability of one mineral to leave a scratch on the surface of another depends on its hardness. Hardness characterizes the resistance of a mineral to destructive mechanical stress on its surface. Hardness is of great importance for stones used in jewelry so that they do not break down quickly when worn. This resistance is due to the structure of the crystal and the strength of the chemical bonds. Hardness decreases with defects and inhomogeneous structure of the stone.

The ordinal number or coefficient is determined as follows: if any mineral scratches, for example calcite, having a hardness of 3, then its hardness is indicated by a factor of 3.5 (or 3-4).