Modern science of precious stones. What does gemology study and who is a gemologist?

Stone is any hard, non-malleable component of the earth's crust in the form of a continuous mass or individual pieces. A jeweler understands precious stones by this word, a builder understands materials with which streets are paved and houses are erected. Geologists involved in Earth science call the objects of their study not “rocks,” but rocks and minerals.
A rock, or, as it is more often said, rock, is a combination (aggregate) of minerals of natural origin. Typically, rocks comprise more or less significant areas. Sand and loam are also classified as mountain (more precisely, loose sedimentary) rocks. The science that studies rocks is called petrography.
A mineral is an internally homogeneous, solid component of the earth's crust, formed naturally. With the beginning of the era of space flights, the solid components of rocks on the Moon began to be called minerals. Most minerals are isolated in the form of crystals that have certain shapes. The word “mineral” comes from the Latin word mina (“mine”) - mine. The science of minerals is called mineralogy.
A crystal is a body of homogeneous composition of a strictly geometric shape with a regular internal structure - a crystal lattice. The structure of the crystal lattice determines the variety of physical properties of crystals, and thereby minerals. The branch of science that studies crystals is called crystallography.
Gemstone is a concept that does not have a single definition. Most often, precious stones include beautiful and rare minerals (in some cases, mineral aggregates), which have a fairly high hardness and are therefore very resistant to abrasion, in other words, almost timeless. But, of course, the idea of ​​the beauty of a stone has changed over time, which is why certain stones, previously considered precious, have long been forgotten, while other minerals are now, on the contrary, elevated to the rank of precious stones. The concept of a semi-precious stone, as not very hard jewelry and semi-precious stones were previously called, is even less clear and today is not entirely valid. Jewelry stone is a collective concept that covers all stones used as jewelry (including for decorative purposes). In a narrower sense of the word, ornamental stones are relatively inexpensive gems, which are thus, as it were, contrasted with “real” precious stones. The science of precious stones is called gemology.
Ore is generally a mineral mixture with industrial metal content. Recently, some types of non-metallic mineral raw materials that have useful properties are sometimes called ores. Since the practical value of ore (in other words, condition, suitability for development) depends on factors that may change over time (technical capabilities of mining and enrichment, economic conditions, transport conditions), the concept of “ore” is applicable not only to certain minerals or mining breeds

Minerals

Currently, about 3,000 minerals are known, and every year scientists discover more and more types of them. Only about 100 minerals are of relatively great practical importance: some due to their widespread occurrence, others due to special properties valuable to humans. And only a quarter of them play a significant role in the composition of rocks.
Some minerals were known back in Ancient Greece. However, the scientific way of knowing them was established much later. The German scientist Georg Agricola (1494-1555) is rightfully considered the father of mineralogy. A significant contribution to the development of the study of minerals was also made by the professor of mineralogy of the Freiberg Mining Academy Abraham Gottlob Werner (1750-1817), who developed the classification of rocks, and the professor of chemistry from Berlin Martin Heinrich Klaproth (1743-1817).
The emergence of mineral names does not follow any single system: some of them are borrowed from the jargon of miners or folk speech, others were invented specifically. The role of German scientists in the development of mineralogy was reflected in the significant spread of German terms, which received international recognition. Over time, many minerals received new names, but their old names often did not go out of use either. Therefore, now the same mineral can have several names. The nomenclature of precious and ornamental stones is especially confusing: their numerous names are vast and can often be misleading. And although there are international agreements on a unified nomenclature for precious stones, practice shows that even today there is no end to the arbitrary assignment of a variety of trade names to them.

Origin and structure

Minerals can form in different ways. Such well-known minerals as feldspar, quartz and mica crystallize from fiery liquid melts and gases mainly in the bowels of the Earth, less often - from lavas that erupted onto the earth's surface. Some minerals are formed from aqueous solutions or arise with the participation of organisms, some - by recrystallization of existing minerals under the influence of high pressures and high temperatures.
Many minerals often occur in certain communities, or associations, so-called parageneses (for example, feldspar and quartz), but there are also minerals that are mutually exclusive (for example, feldspar and rock salt).
Most minerals have a specific chemical composition. Although the impurities contained in them are capable of influencing the physical properties of minerals or even changing them, they are usually not mentioned in chemical formulas. When identifying minerals, the shape of their crystals plays a very significant role. And although it is not always perfectly expressed in samples, and more often than not it is simply distorted, in most cases it is still possible to distinguish any signs of a crystalline structure - edges, shading or constant angles between faces. Typical crystal shapes are grouped into seven crystallographic systems called systems. The distinction between them is made by crystallographic axes and the angles at which these axes intersect (see table on page 11).
The following crystallographic systems (systems) exist: cubic (regular), tetragonal (square), hexagonal (hexagonal), trigonal (rhombohedral, or triangular), orthorhombic (sometimes called orthorhombic), monoclinic and triclinic.

In the cubic system, all three axes have the same length and are oriented mutually perpendicular. In a tetragonal system, all three axes are mutually perpendicular, two of them have the same length and lie in the same plane, and the third differs from them in length. There are four axes in the hexagonal system; three of them are located in the same plane, have the same length

noy and intersect at angles of 120° (or 60°), while the fourth axis (of a different length) is oriented perpendicular to the other three. The trigonal system has the same axes and angles as the hexagonal system. Therefore, these two systems are often combined into one - hexagonal. The difference between them is manifested in the elements of symmetry. In the hexagonal system, the cross section of the prismatic basic shape is six-
coal, in trigonal - triangular. By cutting off the corners of a triangle, a six-sided hexagonal shape is obtained. In the rhombic system, all axes are mutually perpendicular, but have different lengths. In a monoclinic system of three axes of different lengths, two are mutually perpendicular, and the third is located at an acute angle to them. In the triclinic system, all three axes are different in length and inclined relative to each other.
Of course, most crystallized minerals do not occur as properly formed crystals; More often than not, their forms are distorted and they are characterized by the preferential development of some facets at the expense of others. However, the angles between the corresponding faces always remain the same. Some mineral substances crystallize in different systems. In such cases we talk about polymorphism and polymorphic modifications. For example, calcium carbonate CaCOe can form two modifications under different conditions: trigonal calcite and orthorhombic aragonite.
The factors that determine the shape of a mineral are the structure of its crystal lattice and the packing of atoms, ions or molecules. If, with the same chemical composition, the atoms themselves are always identical, then their relative positions can be very different. The structure of the crystal lattice determines not only the shape of the crystals, but also their cleavage. So, for example, with a spiral arrangement of particles in the lattice, which does not allow flat interfaces to be drawn in it, the crystal does not split along the cleavage (that is, it has no cleavage).
All crystalline minerals have a lattice, and only the internal structure of amorphous substances is devoid of regular order.
In some cases, as a result of the creation of cavities remaining in the place of dissolved and removed crystals, replacement or overgrowth (crustification) of other formations, minerals may appear in crystalline forms that are atypical for them - in the form of so-called pseudomorphs, or false crystals.
If minerals of the same structure differ only in minor variations in chemical composition, changes in color, or some other features, they are said to be varieties. Among precious and ornamental stones, varieties play a significant role.
A cut or faceting is the combination of faces that is most characteristic of crystals of a particular mineral (for example, the rhombic dodecahedron of garnet), while habit is the appearance of crystals and their aggregates (for example, columnar, tabular or acicular). Seemingly structureless mineral masses composed of crystalline grains that have a lattice, but due to difficult growth are deprived of correct external restrictions, are called confluent, continuous or massive granular aggregates.
Sometimes two or more crystals of one mineral grow together in such a way that they exhibit a regular mutual orientation. Similar

formations are called twins, tees and complex (multiple, multiple) twins. Along with intergrowth twins, in which the constituent crystals only touch each other (along the intergrowth plane), there are also intergrowth twins with mutual penetration of their constituent crystals into each other. Twin intergrowths are recognized by the reentrant angles that are often observed in them, which never appear in single crystals.
Large and well-formed regular crystals of beautifully shaped minerals are found in rocks, where they grow on the inner walls of rounded closed cavities. Such voids filled with mineral matter are called geodes, and groups of beautiful crystals that have grown on their walls or on the walls of cracks are called druses. Typical drusen minerals are quartz, calcite and fluorite.

Collectors call free (or prepared) well-formed mineral groups ores. But for the most part, crystalline individuals are so small that they can only be recognized under a magnifying glass or even a microscope. Such crystalline (granular) aggregates are called dense.
Of particular interest to the collector are the so-called stone roses - leafy growths that arose as a result of the displacement of individuals that initially grew on top of each other in a parallel position. Similar coarse leafy forms of “rose” type development can be found in gypsum, barite and hematite (iron mica).
Much more common are various types of mineral intergrowths (mineral aggregates or mineral accumulations). Depending on the mineral composition and the conditions under which the growth process took place, columnar, radially oriented (radiant, fibrous, acicular, etc.), leafy or granular aggregates arose. Radial aggregates tend to form spherical shapes, which, when they have a smooth and shiny surface, are called glass heads (more correctly called "bald"). Concentric shell-like formations, such as aragonite pea stone, are called oolites (see page 16).

Physical properties

In minerals, the shape of crystals in most cases is not so ideally developed that it can be used to accurately distinguish one mineral from another, so here we are helped by such physical properties of minerals as color, luster, cleavage, fracture, hardness and density.
However, the amateur should remember that not all minerals he encounters can be diagnosed without resorting to special chemical and physical studies.

Color and trait

The color of a mineral can only in rare cases serve as a characteristic diagnostic sign, as, for example, in blue azurite, green malachite, yellow sulfur or red cinnabar. Most mineral species can have different

coloring For example, fluorite can be colorless, yellow, brown, pink, green, blue, purple and even almost black. Chemical and mechanical impurities can change the natural color of the mineral and make it possible to distinguish its varieties.
In addition, the color shades of minerals can change under the influence of high temperatures, ultraviolet and radioactive radiation, and simply fade in sunlight. In jewelry, artificial coloring of precious and ornamental stones plays a significant role.
A more reliable diagnostic feature of minerals than color is the so-called trait color (or, as is often said, simply the trait). The color of the line is revealed by rubbing a piece of unglazed porcelain—a sponge cake—with a corner of the test sample. If the mineral turns out to be hard, it is recommended to first scrape off some of the powder with a file, and then grind it on a plate.
The line reflects the mineral’s own color; its color is more constant and less dependent on the color varieties of the mineral. Thus, the color of black iron luster (a type of hematite) is cherry-red, golden-yellow pyrite is black with a greenish tint, and fluorite, regardless of its yellow, green or purple color, is always white.

Shine, transparency

A mineral's luster is caused by the way light reflects off its surface. In mineralogy, glassy, ​​silky, pearlescent, diamond, greasy, resinous, waxy, metallic and semi-metallic luster are distinguished. Many minerals lack any shine at all; they appear dull and matte. Metallic luster occurs not only in native metals, but also in sulfides, as well as in some oxides. Many minerals with a metallic luster exhibit tarnished colors, and in such cases they often exhibit magnificent iridescence.
Plaques and surface weathering phenomena can change the luster of a mineral or significantly reduce it. Therefore, the definition of gloss is also not always unambiguous.
Minerals can be transparent, translucent, that is, weakly transmitting light, or opaque. The latter include minerals with a metallic luster. However, almost all minerals, with the exception of native metals (except gold), are transparent or translucent in very thin sections called thin sections.

All light-transmitting minerals that do not belong to the cubic system exhibit more or less strong birefringence. If, for example, you put a rhombohedral calcite crystal on a page with some text, then all the letters will be visible through the crystal, forked. Iceland spar (a transparent variety of calcite) exhibits the phenomenon of birefringence especially clearly, and therefore this mineral is also called birefringent spar. However, in most minerals the birefringence of light is so small that it cannot be recognized by the naked eye. The reason for birefringence is that a ray of light passing through a crystal is split into two rays, each of which is refracted differently.
In some minerals (mainly precious stones) you can see shimmer, flicker and other light effects (iridization, opalescence). These optical phenomena arise due to the reflection of light from thin plates, which are inclusions in the mineral or are directly involved in its structure. (Opalescence is caused by the scattering of light on layers of tiny silica beads. - Trans.)

Cleavage and fracture

Many minerals fracture along flat surfaces. In such cases, the mineral is said to have cleavage. Cleavage depends on the structure of the crystal lattice. Depending on the ease with which the mineral splits, a distinction is made between very perfect (mica), perfect (calcite) and imperfect (garnet) cleavage. All spars (feldspar, fluorspar, fluorite spar, calcite spar) are distinguished by good cleavage. But there are also minerals that lack cleavage at all (quartz). In such cases, the separation of adjacent individuals from each other in fused twins is called not cleavage, but separateness.
For minerals that have poor cleavage or no cleavage at all, an important diagnostic feature can be fracture - the nature of the surface of irregular fragments into which the crystal splits upon impact. There are conchoidal, splintered, fibrous, smooth, uneven, stepped and earthy fractures. Conchoidal fracture is typical of all varieties of quartz and of all glassy rocks.

Hardness

The hardness of a mineral usually refers to the resistance that its surface exhibits when you try to scratch it with another stone or other object.
German mineralogist Friedrich Mohs (1773–1839) proposed a scale that groups minerals according to their relative hardness on a scale of ten, called the mineralogical hardness scale, or Mohs scale. Each mineral occupying a certain place on this scale scratches all minerals with a lower hardness value, but at the same time it is itself scratched by harder minerals above it. Minerals with equal hardness values ​​do not scratch each other.
By comparison with this scale, the hardness of any mineral can be determined - Mohs hardness. “Minerals with a hardness of 1 and 2 are considered soft, 3 to 6 are considered medium hard, and above 6 are considered hard. Minerals with a hardness of 8 to 10 are said to have the hardness of precious stones.
The Mohs scale is a relative scale. With its help, it can only be determined which mineral is harder. It is impossible to say how hardness increases in quantitative terms from step to step on the Mohs scale. In the table presented here, this scale is compared with absolute hardness values ​​- this is the hardness of grinding in water according to Rozival. A comparison shows how the absolute hardness increases abruptly. For a non-specialist, determining absolute hardness, which requires complex equipment, is almost impossible.

Scale hardness		Mohs hardness	Hardness grinding
		Scratch with a fingernail
		Scratched with a fingernail
		Scratched by a copper coin
		Easily scratched with a pocket knife
		Difficult to scratch with a penknife
	Orthoclase	Scratched by a file
		Scratching window glass
		Easily scratches quartz
		Topaz scratches easily
		Doesn't get scratched by anything

When determining Mohs hardness, samples with sharp edges should be used and scratched on timid, fresh (unaffected by weathering) surfaces. For ribbed formations, leafy crystals, and minerals weathered from the surface, the scratch hardness values ​​are underestimated. The application of the Mohs scale to rocks is generally impossible due to their heterogeneity - the presence of dissimilar components.
The main advantage of the Mohs scale is its ease of use. With the help of reference samples and scratch kits, mineral hardness can be easily determined in the field, during walks and excursions. Even if you don’t have control samples at hand, you can use other simple aids. Thus, our fingernail scratches minerals with a hardness of up to 2, a penknife with a hardness of up to 5-6, glass is easily scratched by quartz (its Mohs hardness is 7). Of course, for professional diagnostics of a mineral or gemstone, the Mohs hardness test is too imprecise. In addition, gemstones can be damaged when scratched. Therefore, in such cases, they resort to determining the so-called grinding hardness, which is measured by the amount of mineral that is ground off from the surface of the sample under certain conditions.

Density

Density refers to the mass of a substance divided by the mass of an equal volume of water. Therefore, a mineral with a density of 2.6 is 2.6 times heavier than the same volume of water. The density of minerals, rocks and ores ranges from 1 to 20. Minerals with a density below 2 are perceived as light (amber - 1.0), from 2 to 4 - as normal (quartz - 2.6), above 4 - as heavy ( galena, or lead luster - 7.5).
The most expensive gemstones, like precious metals, have a higher density than rock-forming minerals such as quartz and feldspar. For this reason, in flowing waters, first the deposition and accumulation of heavy minerals occurs, and then the quartz sands that cover them. These types of deposits of useful minerals are called placers.
The density of a mineral can be calculated as follows:

The mass of a mineral can be easily determined using any scale. Its volume can be found in a variety of ways, including by displacing water in a measuring vessel or by hydrostatic weighing. The second method is more accurate and suitable even for small samples. On a hydrostatic balance, a mineral suspended on a thin wire is first weighed in air and then immersed in water. The difference between both results corresponds to the mass of displaced water and is thus numerically equal to the volume of the mineral. This method of determining density with an accuracy of one decimal place is also accessible to an amateur. Of course, it is important to ensure that the mineral is clean and free from foreign substances of a different density.

Weight when weighed in air
Weight when weighed in water Difference (volume)

The density of this sample is 2.7; Judging by this figure, the identified mineral is calcite.

Other properties

There are also other properties and methods that can help in identifying minerals, such as their behavior in front of a blowpipe and in transparent sections, magnetism, smell, taste, and feeling to the touch.
Fusibility and flame color reaction tests are carried out using a blowpipe. It is a brass tube with a wooden mouthpiece at one end and a hair hole at the other. By blowing air through a blowpipe into a flame (for example, a Bunsen burner or even an ordinary candle), you can make it very hot and beam it to the desired point. To use a blowpipe effectively, laboratory aids are required, as well as some chemistry knowledge and skills. Therefore, non-specialists should use the blowpipe method only as an exception.
Transparent sections (sections 0.02-0.03 mm thick) allow you to examine the structure of the sample under a microscope. Along with polished sections (clear sections), they are used in the study of ores, but they play a primary role in petrography, in the microscopic study of rocks.

Classification

The entire variety of minerals is divided into groups that combine minerals with common characteristics. In scientific mineralogy, it is common practice to classify minerals primarily by their chemical composition. Below are the classes of minerals.

1. Elements: diamond, bismuth, graphite, gold, copper, arsenic, platinum, sulfur, silver.
2. Sulfides: stibnite, argentite, arsenopyrite, orpiment, fahlore, bornite, bournonite, galena, cinnabar, cobaltine, covellite, red silver ore, lellingite, marcasite, molybdenite, nickelin, pentlandite, pyrite, pyrrhotite, realgar, stannite, sphalerite, chalcocite , chalcopyrite, chloanthite.
3. Halides: atacamite, halite, carnallite, cryolite, sylvite, fluorite.
4. Oxides and hydroxides: anatase, braunite, wolframite, hausmannite, hematite, goethite. gibbsite, diaspore, ilmenite, cassiterite, quartz, corundum, cuprite, limonite, magnetite, manganite, opal, pyrolusite, psilomelane, rutile, uranium pitch (pitched pitch), franklinite, chrysoberyl, chromite, zincite.
5. Nitrates, carbonates, borates: azurite, ankerite, aragonite, boracite, witherite, hydrozincite, dolomite, calcite, magnesite, malachite, rhodochrosite, siderite, smithsonite, strontianite, cerussite.
6. Sulfates, chromates, molybdates, tungstates: anhydrite, anglesite, barite, wolframite, wulfenite, gypsum, crocoite, molybdenite, celestine, scheelite.
   
7. Phosphates, arsenates, vanadates: apatite, turquoise, vanadinite, vivianite, lazulite, mimetesite, pyromorphite, uranium micas.
8. Silicates: augite, actinolite, andalusite, arfvedsonite, beryl, bronzite, vesuvianite, wollastonite. Gayuin. hedenbergite. hypersthene, diallag, diopside, dioptase, jadeite, kaolinite, kyanite (disthene), cordierite, lapis lazuli, leucite, montmorillonite, nepheline, noseane, olivine, pyrophyllite, feldspar, prehnite, hornblende, rhodonite, serpentine, sillimanite, sodalite, spodumene , staurolite, talc, titanite (sphene), topaz, tremolite, tourmaline, chlorite, chrysocolla, zeolites, zircon, zoisite, aegirine.

There are other classification principles in mineralogy.
In our case, the basis for the classification of minerals is the areas in which they are of greatest importance to humans, that is, groups of rock-forming minerals, precious and ornamental stones and ore minerals are distinguished.

There are several sciences that study stones from one side or another.
Such a science as mineralogy (German Mineral or French minéral, from Late Lat. (аеs) minerale - ore) studies stones that are classified as minerals. Minerals are characterized by a natural origin and certainly a crystalline, ordered structure, which is the result of various geological processes. Amorphous formations (amber, glass, including volcanic glass) and noble organic materials (coral, pearls, jet...) cannot be classified as minerals.

Closely related to mineralogy gemology (from Latin gemma - “gem, precious stone”, and other Greek λόγος - “word, mind”), the science of gems. The concept of gems is broader than that of minerals, but it cannot be classified as scientific terms; it is of a historical and everyday nature and at different times different stones were classified as gems. According to Fersman, for example, only transparent stones can be classified as semiprecious stones, without making a distinction between precious and semi-precious ones. He proposed to classify the remaining varieties as “colored stones.” Unlike mineralogy, gemology includes as an object of study both minerals and amorphous structures, organic formations and even synthetic stones. The subject of study is the physical, optical, chemical properties of gems, the technical side of their processing and cutting, as well as decorative and artistic aspects.

Another science that used to be part of mineralogy is crystallography (from Greek κρύσταλλος, originally “ice”, later “rock crystal”, “crystal” and γράφω “I write”). Crystals mean a form of formation characterized by a strict structure. One mineral can have several crystal forms, several variants of crystals, and the crystals can also be synthetic.

And finally, there is the science of rocks and their constituent minerals - petrography (from Greek πέτρος “stone” and γράφω “I write”). It is descriptive in nature, studying the textural features and structure of rocks, using optical microscopy and mass spectrometry as the main research methods. Related science petrology (from Greek πέτρος - “stone” and λόγος - “word, mind”) deals with a more detailed study of igneous and metamorphic rocks, including the study of genetic connections between them and the conditions of their formation (as opposed to petrography).

Actually, based on information from these sciences, it is possible to sufficiently understand the huge variety of stones that we use in everyday life or simply come across around us.

Gemology is a branch of mineralogy that studies precious stones. Its task is to study the physical and chemical properties of precious minerals, their optical, as well as decorative properties. A gemologist, using special equipment, can always distinguish a natural stone from a synthetic one, and will immediately determine the imitation of a particular stone. It is no secret that store sellers often do not tell the buyer that the stone is not synthesized. Conscientious manufacturers always indicate on the labels the naturalness of the stone, which cannot be said about trade.

jadeite roses

There are authoritative gemological organizations in the world. The oldest of them, the Gemological Association of Great Britain, was founded in 1908. This is one of the leading gemological institutes in the world. Since 1929, this organization has been training and graduating qualified gemologists. In Russia, gemological research, including stone refining, is carried out at Moscow State University. There are also professional courses for training gemologists here.

red tourmaline crystal

Gemology as a part of mineralogy was born along with the advent of artificial gemstones. This happened at the beginning of the twentieth century, in 1902. This year the French chemist M.A. Verneuil received and offered synthetic rubies, sapphires and spinels for sale. The market immediately reacted to the emergence of competitors. Natural gem-quality stones have risen in price and become available to the richest buyers, while synthetic stones have formed their own niche: cheaper, for less solvent buyers. The art of synthesizing stones developed, and synthetic emeralds and diamonds soon appeared. They are also much cheaper than natural ones.

More than four thousand minerals are known in the world, of which a third are used as jewelry (precious), jewelry, and ornamental stones. Strictly speaking, not all minerals that we call so are minerals. The frozen resin of ancient trees, amber, the skeletons of marine organisms, corals, pearls, the inner surface of shells - mother-of-pearl, a type of coal - jet, volcanic glass - obsidian are not minerals.

And, finally, synthetic stones obtained in factories and laboratories are also not minerals from the point of view of the strict science of mineralogy, since by definition a mineral is, first of all, a “natural crystalline formation.” These are cubic zirconias, synthetic garnets, the synthetic diamonds mentioned above, rubies, emeralds, quartz, spinel and many other analogues of natural minerals.

During the development of mineralogy, several different gemological classifications were proposed. Currently, most gemologists use the classification given below by E.Ya. Kievlenko.

This classification is a general option and does not include all minerals used in jewelry and stone cutting. In addition, some minerals, for example, alexandrite, are classified by different specialists in different sections.

Gemological classification adopted in Russia

(Classification by E.Ya. Kievlenko, based on the method of use and cost of stones)

Jewelry (precious) stones

I order: diamond, ruby, emerald, blue sapphire.

II order: alexandrite, noble jadeite, orange, yellow, purple, green sapphires, noble black opal.

III order: demantoid, noble spinel, noble white and fire opals, topaz, aquamarine, red tourmaline, rhodolite.

IV order: blue, green, pink and polychrome tourmalines, noble spodumene (kunzite, giddenite), zircon, yellow, green, golden and pink beryl, turquoise, peridot, amethyst, chrysoprase, pyrope, almandine, citrine.

Jewelry and ornamental stones

I order: smoky quartz, amber-succinite, rock crystal, jadeite, jade, lapis lazuli, malachite, aventurine, charoite.

II order: agate, colored chalcedony, cachalong, amazonite, rhodonite (eagle), heliotrope, hematite-bloodstone, rose quartz, iridescent obsidian, common opal, labradorite, other opaque iridescent feldspars.

Ornamental stones

Jasper, written granite, petrified wood, marble onyx, larchite, obsidian, jet, jaspilite, selenite, fluorite, aventurine quartzite, agalmatolite, cut stone, colored marble.

Description:

In the jewelry business, a gemologist is the “number one figure.” A professional gemologist can easily determine the type of gemstone and its origin, distinguish synthetic analogues and imitation gemstones from natural gemstones.

Gemology is a science that studies the chemical composition of precious stones, their physical properties, and the quality of jewelry. Accordingly, a gemologist is involved in identifying, evaluating and certifying gemstones. A professional gemologist can easily determine the type of gemstone and its origin, distinguish synthetic analogues and imitation gemstones from natural gemstones. To do this, a gemologist must know the methods of refining precious and ornamental stones. His main tools are his eyes, magnifying glass, microscope, refractometer and spectroscope. This is a rather rare and therefore in-demand profession, both in our country and abroad.

The profession of a gemologist is quite complex, but at the same time very interesting and unusual, because only a gemologist can admire the beauty and uniqueness of diamonds, while giving a competent assessment of their merits

Interesting Facts

Diamond prices depend on their quality parameters, and the difference between two diamonds of the same weight can be very impressive. The rating of diamonds consists of a combination of four Cs - Carat, Color, Clarity, Cut, that is, the parameters of weight, color, transparency and cut quality. The classification of diamonds based on these characteristics is called “4C”.

Carat (weight). The weight of a diamond is measured in carats. 1 carat is equal to 0.2 grams. There are three weight groups of diamonds: small, medium and large. The weight of small stones is up to 0.29 carats, medium diamonds vary between 0.3 and 0.99. Stones larger than 1 carat are considered large.

Color There are traditional color (or Cape) diamonds and fancy color diamonds. The first group includes colorless diamonds and the entire color scale of yellow shades. Moreover, the most valuable are the so-called “pure water diamonds,” that is, colorless, and the least valuable are stones with a strong yellow color. The exception is rare gold and black diamonds. The second group includes green, blue, pink, red, blue diamonds, etc. The fancy color of a diamond can be natural - as a result of mineral impurities during the formation process:

pink color - an admixture of manganese,

blue color - the presence of boron,

the black shade is graphite,

blue color - an admixture of aluminum,

green tint - the presence of chromium,

yellow color is lithium,

brown tint - iron particles.

Clarity (transparency, purity). Clarity is the most significant parameter of diamond quality and is expressed in the presence/absence of defects and foreign inclusions in the structure of the stone. In this case, defects can be both internal and superficial, that is, which can be eliminated by grinding. To determine the number and size of inclusions, a 10x magnifying glass is usually used. To assess the transparency of diamonds, the Russian system TU 25-07.1319-77 and the international GIA system are used.

Cut (cut). When judging a cut, the fundamental principle is not its shape (round, princess, pear, heart, emerald, asscher, marquise, etc.), but the quality of execution. The degree of its brilliance and play of light depends on how geometrically accurately and proportionally the diamond is cut. The ideal cut is designated by the letter A, then in a process of decreasing quality.

List of stones that gemologists work with

Currently, more than 4,000 minerals have been discovered in nature. Of these, less than 350 are used in jewelry. A gemologist in his work encounters the following materials, both cut and unprocessed:

1. Common cut stones: diamond (diamond), emerald (green beryl), ruby ​​and sapphire (corundum of different colors, transparent or star-shaped), spinel, noble opal, fire opal, aquamarine (blue beryl), heliodor (yellow beryl) , topaz, tanzanite (blue zoisite), tourmaline (mineral group), peridot (olivine, peridot), zircon, garnets (mineral group), amethyst (purple quartz), citrine (yellow quartz), rauchtopaz (brown quartz), morion ( black quartz), rock crystal (colorless quartz).

2. Stones of organic origin: pearls, amber, coral, jet.

3. Cut stones are relatively rare: alexandrite (chrysoberyl with the effect of changing color), axinite, actinolite, andalusite, apatite, sparrowite (pink beryl), vesuvianite, giddenite, danburite, datolite, diopside, cordierite, kyanite, cornerupin, kunzite, scapolite, sphene, chrysoberyl, chrome diopside, enstatite, epidote, euclase.

4. Ornamental stones: aventurine, agate, amazonite, turquoise, heliotrope, hematite, jadeite, carnelian, quartz, cat's eye, labradorite, lapis lazuli, moonstone, malachite, moldavite, jade, obsidian, petrified wood, onyx, opal, mother-of-pearl, feldspars, prazem, rhodonite, carnelian, serpentine (coil), ivory, hawk's eye, sunstone, tiger's eye, uvarovite, chalcedony, chrysoprase, charoite, jasper.

5. Synthetic analogues of natural stones: diamond, emerald, ruby, sapphire, alexandrite, spinel, noble opal, amethyst, citrine, rock crystal, rutile, scheelite, turquoise, malachite, coral, as well as cultured pearls.

6. Imitations: glass, plastic, epoxy resin, bakelite, cubic zirconia, yttrium aluminum garnet (YAG), gallium gadolinium garnet (GGG), lithium niobate, strontium titanate, yttrium aluminate, zincite.

7. Refined natural stones and synthetic materials mentioned above.

Collectible stones include rare stones that are not always suitable for use in jewelry. Their names do not mean anything to a non-specialist, but a gemologist often encounters them - these are, for example, eudialyte, californite, and brazilianite.

Place of work

Gemologists are involved in the production and trade of stones and jewelry.

Material used in preparation Occupational Guide: list of professions and their descriptions

Responsibilities:

· sorting of stones (by size, shape and quality);

· selection of sets of stones;

· selection of stones for repairing products;

· registration of invoices;

· calculation of the price of incoming products;

· evaluation of stones in products (characteristics);

· control of current stone residues;

· control of delivery times of stones from suppliers;

· analysis of information on suppliers' prices;

· making proposals for purchases;

· accounting of stones by groups and sizes;

· preparation of gemological descriptions for incoming products;

· reconciliation with production.

Requirements:

Important qualities

· acute vision

good color perception

· perseverance

· high concentration of attention

· stress resistance

· responsibility

Education

To become a gemologist, you need to enroll in the Faculty of Geology or Mineralogy and in the fifth year choose the specialization “Gemology” or the corresponding department. There are gemologists with a colored and a white diploma. The first is given to a gem specialist, the second to a diamond specialist.