Gemmology

Artificial Christmas Tree

Gemmology - a science about semi-precious stones. By semi-precious stones mean bunch of natural formations in which one the youngish science - a gemmology intimately bundled to a mineralogy is engaged, petrography and a crystallography, except methods of the pointed sciences it uses methods of physics, chemistry, petrology, geology and zoology. The close connection with a mineralogy is spotted by that the overwhelming majority precious and ornamental stones is represented by minerals. From more than 4 thousand known minerals third is immediately used in jeweller business, and the others can serve ornamental, lining or is expositional - a museum stuff. However not all precious and ornamental stones - minerals. By definition, the mineral is the natural chemical combination of a crystal structure formed during various geological processes. Minerals are not some amorphous formations - amber or volcanic glasses, but they installations of analysis of a gemmology. Do not fall into to minerals and noble organic yields: pearls, a coral, gagate, etc. At last, minerals are not the semi-precious stones gained synthetic by in labs and on production plants (recently them there was an assemblage), are phianites, yttrium - aluminium and gallium - Gadolinium grenades, synthetic diamonds, emeries, quartzes and assemblage of other synthetic analogues of natural jeweller rocks.

Gemmology main routes are:

The descriptive
Aesthetic, emotional
The genetical
Applied and technical and economic
The experimental
The regional

The practical gemmology is engaged in all aspects of treatment of rocks - cutting, upgrading, painting, etc.

Gemmology purposes and problems

The primary goals of a gemmology are:

Application of non-destructive instrumental research techniques of material to analysis of precious stuffs
Analysis of ornamental properties and idiosyncrasies of colour rocks for the purpose of their use for manufacturing of ornaments, ornamental subjects or works of art
Perfection of processes of upgrading of juvelirno-ornamental raw

Gemmology main objectives are:

Mining of measure of diagnostic of natural and synthetic semi-precious stones
A heading in jeweller business of new colour rocks and spreading of possibilities of use of already known minerals
Building of new synthetic analogues of minerals and ornamental stones, and also perfection of flow diagrammes of synthesis of already existing semi-precious stones

Installations of immediate observations and object of research

Subject of my explorations are the rocks decorating our life which one have gained the name semi-precious stones and colour rocks. These are manifold minerals on makeup and the rocks possessing natural decorative effect (beautiful painting or drawing, transmittance, bright luster, a light play or other, quite often combining properties) and, besides giving in to certain tooling (to kerf, cutting, sanding, polishing).

Only certain variety of minerals which one differ any choronomic sign, more often painting, the moulding box of crystals, outward and morphological characters happen installation of immediate observation in a gemmology often.

Installations of immediate observations and object of research

Up-to-date knowledge in a gemmology

Classification of colour rocks

In gemmology development the assemblage of classifications jeweller, ornamental and facing stones was offered. We will observe one of them - classification of colour rocks on which one refer the majority gemmologist and which one ground is the measure of cost of semi-precious stone. According to this classification, colour rocks are divided into 3 bunches:

Jeweller (precious) rocks
Jewellery - ornamental stones
Ornamental stones

In turn, these bunches are divided into orders:

The first bunch
- 1st order: diamond, an emerald, ruby, sapphire cyan.
- 2nd order: an alexandrite, orange, green and violet sapphire, noble black opal, noble jadeite.
- 3rd order: a demantoid garnet, a spinel, noble white and fiery opal, aquamarine, a topaz, rhodolite, a tourmaline.
- 4th order: chrysolite, zircon, yellow, green and pink beryl, a kunzite, turquoise, an amethyst, pyrope, an almandine, a lunar and solar rock, chrysoprase, a citrine.
The Second bunch
- 1st order: lazurite, jadeite, axe-stone, malachite, a charoit, amber, rock crystal (smoky and uncolored).
- 2nd order: an agate, an amazonite, haematite - a bloodstone, the rhodonite, opaque iridescent felspars (a moonstone, etc.), "iridescent" volcanic glass, an epidote - garnet rodingites (jadeites).
The Third bunch
- Jasper, marble onyx, volcanic glass, gagate, fossil arbour, listvenite, graphical pegmatite, fluorite, quartzite, selenit, agalmatolite, colour marble, etc.

In bunch Jewellery - ornamental stones solid and most beautiful opaque rocks are merged, best of which one are used along with jewels in jewels, and ordinary raw - in mass ювелирно - notions and suvenirno-stone-cutting effecting. Besides, abundant enough transparent rocks refer to to this bunch - amber and rock crystal (smoky and uncolored), standing much more low, than rocks of IV order.

It is necessary to remember, that the produced classification (however, as well as any another) cannot be considered as the universal. Cost of a colour rock is spotted by assemblage of variating factors, for example a mode. In this connection disalignment of separate semi-precious stones both downwards, and hill up under classification orders is is possible. The alexandrite - very rare variety of a mineral of chrysoberyl (BeAl₂O₄), changing the painting depending on the nature of a radiant of illumination is rather indicative in this respect. Last years many gemmologists refer to an alexandrite to the first order of the first bunch, sizing up its cost frequently above diamond, ruby, sapphire and an emerald. I wish to tell about this remarkable rock a little.

Alexandrite

Alexandrite - the most valuable variety of a mineral of chrysoberyl. For the first time has been detected 1834 in Urals Mountains. For today the alexandrite is mined in Brazil, by Zimbabwes, on Madagascar. There is it also in India and Southern Africa. In jewels this mineral meets exclusively rarely. It is bundled to high cost and a rarity of a qualitative alexandrite. The alexandrite is easy enough for distinguishing from other similar minerals on optical properties by means of foolproof instruments. And here the alexandrite of a synthetic parentage can be distinguished only in laboratory requirements.

The cost appraisal of an alexandrite is influenced by following measure: capacity to variate the colour depending on light conditions, colour of a rock, purity, cutting and weight.

Capacity to discolour is termed "run-down". It is sized up in a percentage ratio (on colour how many is strongly inflected). The more a run-down, the more expensively a rock.

Colour is sized up in two aspects of illumination: at diurnal and electrical light. The alexandrite changes colour over the range: at an outdoor lighting from slightly bluish-green to yellowish-green, at electrical - from orange-red to sirenevo-red. The most valuable colours of an alexandrite are: at an outdoor lighting green, at electrical - red and slightly sirenevo-red. Purity also influences cost - the less pluggings, the more expensively a rock. Theoretically pure alexandrite is very rare, in most cases it is driven by multiple concretions and fractures. To this sign it is easy to distinguish synthetic emery with effect of changeover of colour in which one pluggings routinely are not present. At a cutting appraisal rock geometric proportions, quality of a polish, presence of spallings and the fractures croping a rock are allowed.

Weight is sized up in karats - the more weight, the more expensively a rock.

There are alexandrites effect of "the cat's eye". Such variety is termed - a cymophane. The cymophane is treated in the form of a cabochon. The alexandrite with effect of the cat's eye is appreciated much more low.

Cutting of jewels

Semi-precious stones the nature has presented much with perfect blazing basils, an amazing play of light. But all the same the jewel moulding box is not capable to open its charm completely. Because of affecting of an atmospheric precipitation, underground waters and various gases of a basil of crystals are coated with notches, primes, poles. They not only mask charm of semi-precious stones, but also make apparent impression about their ordinariness. In the nature it is difficult to detect a crystal without any flaws, and the more a rock, the latent defects - microseparations, foreign substances in the form of chips or air blisters are more multiple.

Bright, blazing on the sun all tinctures of colour gamma semi-precious stones from an extreme antiquity drew attention of the human. And to make their beautiful, masters tried to refine and polish with various means of a basil of rocks. Then they blazed in sun beams, as the clearest semi-precious stones.

Stone carving art, or glyptics is a manufacturing гемм. Engraved on a surface of rocks protuberant images are termed as a cameo, and profound images - an intaglio.

Hollow barrels from chalcedony or an agate on which one figured symbolical signs and religious figures were the most ancient stone-cutting products. Such barrels served as printings or amulets. The most ancient look-alike subjects it come from the states Dvurechja - Sumerians, Babylon and Assyria prospering long before invasion of our chronology. The first carved figures from a rock, introducing dung beetles or scarabs, have occurbed several millenia ago. Them especially esteemed in Ancient Egypt.

The glyptics were eurysynusic in Antique Greece. Very much this art has attained a high level in days of Ancient Rome. But in the Middle Ages it is art it has been forgotten. Only in Renaissance artists of Italy were converted again to stone carving. Now the glyptics are very popular all over the world. The centre of stone-cutting art in Europe considers Idar-Oberstein in Germany, whence enters on the market of the Western Europe about 90 % of carved rocks.

If earlier for manufacturing of gemmae used various agates on painting, jaspers, is rarer - amethysts gradually in glyptics orbit began to be involved and other rocks. And not only ornamental, but also precious. And now even on diamond basils it is possible to see the various engraved figures.

In an antiquity, shaping rocks, routinely only ground and glazed natural basils. Thus, luster and rock scintillation were attained. The polished rocks strung on a thread and wore on a neck in the form of a necklace or a pendant. In especially relevant cases as, for example, at manufacturing of the ring for the High priest, the jeweller should select a rock fitting on colour and sizes, certain demands, and even to it a casing. By the way, unlike our days a casing selected long and very carefully.

The most popular mean of giving of the moulding box to a rock is termed "cabochon" that "head" means. In ancient Rome was considered, that such rocks help the humans, suffering short-sightedness. It is bundled, it that the transparent rocks in the form of the complete cabochon represent concave lens. Emperor Neron observed fights of gladiators through an emerald cabochon about what writes in compositions Pliny the Elder.

Cabochon mean treated emeralds, ruby, sapphires and grenades. Today all these rocks cut, and the cabochon moulding box attach only having any flaws. The cabochon treats "the cat's eye", stellar rocks or Asteria and, mainly, semi-transparent and opaque rocks. An Asteria are cyan (stellar sapphire) or red (stellar ruby) emeries. At cutting in these rocks at the conforming illumination there is a six-beam spider. To the Dark red garnet as which one termed as a carbuncle earlier, so often shaped a cabochon, that this name became its synonym. In the middle of the last century it was the most popular rock for brooches. Now it becomes fashionable again.

Cabochons happen three types to gradation from one to another. The first type: the correct moulding box a protuberant cabochon without basils. Both surfaces of a rock, top and bottom, are incurvated, and both cambers have an equal sign. At cutting of lunar and stellar rocks a suction face usually more protuberant, that promotes the best optical effect. To ruby or sapphire of the penetrating pink or blue tinctures attach the lineaments reinforcing light emission of a rock.

Disgraces always do by more protuberant on the open side. Chrysoberyl "the cat's eye" treat with an establishment cobble. It reinforces all, colour and maintains a rock virgin stock.

The protuberant cabochon at an opposite side deplanation transfers in the second type simple cabochon (like the fallen asleep drip of lard). At it bottom face always the plane. This most ancient moulding box is routinely used for quartzy “the cat's eye”, and sometimes and for red garnets.

At changeover of curvature of bottom face there is a cabochon of the third type - convexo-concave. On bottom face a getting is thus formed. Such mean is is more preferential at treatment of dark rocks, for example, densely coloured carbuncles.

At facet cutting all rock coat with plane faces. Before this moulding box spotted secular character and underlined magic force of a rock. There is four variety of facet cutting:

The diamond table: in the form of a thin lamina with a major plane face from above
Rose: assemblage of triangular and rhomboid basils form bulge in the form of a flying drip on the plane establishment (so, for example, the rose of Antwerp contained 12 basils, a rose with a red parenthesizing - from 12 to 24 basils)
Diamond, or diamond, cutting is carried out in the form of two truncated pyramids compounded by the establishments from which one one looked an apex hill up, another - an apex downwards and all this construction is put in into a casing
Cutting by "short flight of stairs" is close under the moulding box to a truncated pyramid, but the apex and a lateral face are executed in the form of a trapezoid

The long time was considered, that diamond cannot be treated because of its extremely major hardness. Therefore up to the XX-th century diamond octahedrons simply put in into casings. For the first time to grind basils of diamonds metallical disks with diamond dusts of kickoffs in XIX century Louis de Berquin from a city of Brugge in Belgium though it is is quite possible, that this mean has arisen in India. The first lapidaries took so a great interest in the power over diamonds that fantastic moulding boxes began to attach rocks. However thus they did not realise, what unique possibilities of the rock.

Up to second half XVI century to rocks in Europe attached only correct moulding boxes of a diamond nose-piece and the diamond table. Both these moulding boxes are grounded on use of a correct octahedron. Primitive tools and lack of a diamond saw which one has occurbed only 100 years ago, did work of the lapidary heavy and long. After all ground off 1/16 part of all mass of a rock.

In the middle of XVI century on the basis of the diamond table the facet rock with a polygonal stage has been gained after cutting. Four lateral ribs in top and bottom rock parts are ground in such a manner that on their places there are plane facets. This so-called simple, or ordinary, cutting together with two end plains numbers 16 facet.

At the further superposition the facet on lateral ribs originates "dual" cutting with 34 facets and roundish lineaments in the plot. This cutting by a rose, which one invention assign to French cardinal Mazarini, wears his name. Jules Mazarin itself took a great interest in treatment of diamonds and has collected a dazzling collection of jewels which one bequeathed to the French corona. Now the rose cuts only small diamonds.

In the end of XVII century the Venetian lapidary Vinchentso Perutstsi has developed a new aspect of cutting of the diamonds, numbering 58 facet. Though the rock outline thus becomes round, but cutting already comes nearer to the diamond. In India the brilliant had 10 basils, in Old England - 37, in Portugal - to 74. And XX-th century cutting already contains from 80 to 88 basils.

The complete brilliant cut which one has been developed in 1910, plugs not less than 32 facet in a high side and not less than 24 facet in the inferior.

There are also special aspects of cutting with major number a facet: royal - 86 facet, majestic - 102, profile, or princesses, 144 146 facet.

At the same type of an abrasion rather manifold moulding boxes can be attached rocks: heart, the arms, a rundlet.

Upgrading and martempering of quality jeweller and ornamental stones

Rarity - the quality proper in natural raw. The mankind was long since aimed to gain semi-precious stones artificial by, and also to enrich quality of natural semiprecious stones. However only presently became possible to grow syntheticly analogues of diamond, ruby, sapphire, an emerald and other precious minerals. Some materials grown in the technical purposes, also with success began to use in jeweller business, for example yttrium - aluminium and gallium - garnets.

Synthesis of minerals - interesting range of a mineralogy. How enrich quality of bright raw? Upgrading Jewellery - an ornamental stuff perceive artificial martempering of its properties for the purpose of raise jeweller and it is art - ornamental qualities of semi-precious stones. More often upgrading is bundled to mineral decolourization. Humans were engaged in it in an extreme antiquity. At upgrading used honey, various ochres and minium, a blue copperas, primitive acids. With progressing of chemistry impregnating of minerals by various chemical compounds became usual business. Presently after discovering of radioactivity and a X-ray it was revealed, that many semi-precious stones possess capacity to discolour at the ionising bombarding radiation. Now in a gemmology wide experience of upgrading of mineral raw materials is accumulated. In the practical purposes for decolourization of minerals use three types of affecting:

The Impregnation reactive materials
Thermal affecting
The Ionizing bombarding radiation

Let's observe each type of affecting. Rather successful instance all known semi-precious stone turquoise. This difficult phosphate of copper (Cu(Al,Fe)₆[PO₄]₄(OH)₈*4H₂O), losing water, turns pale. Jewellers term this process by a turquoise strain ageing. To avoid age-hardenings, in ancient times turquoise impregnated wax, parrafin, tallow, and presently - the colloidal silicon earth, soluble silicate, various organic resins. An agate, cryptocrystalline, streaky variety of a quartz (SiO₂), more often in the nature meets in the form of incrusted assemblies of grey colour. For painting of agates use chrome inorganic salts (green colour), Ferri lactas (yellow colour), cobalt (cyan colour), nickel, copper and other metals. Often chemical impregnating of agates combine with temperature furnacing: in olden time ordinary-looking grey agates stood in a sugar syrup, and then torrefied in ovens, gaining thus remarkable onyxes, with contrast colour drawing. The agates coloured by old masters cannot be distinguished from the best natural formation samples.

Quality of natural colour rocks can be enriched furnacing. Masters of Urals Mountains, taking from a mineral resources morion crystals (black variety of a quartz), baked them in the paste and as a result furnacing gained perfect yellow crystals of a citrine - undoubtedly, more valuable variety.

Entering on the world market from the countries of Indochina natural sapphires frequently are characterised by too dense black-cyan colour, that essentially reduces their cost. Preheating within several days at temperature more 1000C°, as a rule, allows to make natural sapphires essentially more light.

The ionising bombarding radiation quite often result ins to semi-precious stone decolourization in the opposite direction in comparison with furnacing. Unfortunately, the semi-precious stones irradiated with radioactive chemical elements become radioactive. In gemmological practice arrays - bombarding radiations with radioisotope ⁶⁰Ca are routinely used. For example, a topaz (Al₂[SiO₄](F,OH)) - an uncolored, transparent mineral which one after bombarding radiation becomes brown, blue or green depending on radiation dose. Also diamonds which one at bombarding radiation by radium salts are coloured in green colour, at bombarding radiation by neutrons - in brown, and at bombarding radiation in an electron stream - in blue colour.

Scientific methods and resorts of explorations

There are not few scientific research techniques of semiprecious stones. The science is not necessary on site and gives mankind the new resorts of explorations of a rock. Among up-to-date research techniques in a gemmology now are applied:

The X-ray spectral microanalysis (microprobe), allowing to make exact chemical analysis in local range (point) without material shattering. The method is applied at diagnostic of jewels, clonings, definition of makeups of alloys of metals and features of an elemental composition of materials
The Raman spectroscopy (Raman spectra) is used for material definition, and also definition of makeup of the pluggings which are not croping a rock, without its fault
The Electronic Paramagnetic resonance allows to spot natural rocks to within a field, and synthetic - to within a synthesis method. Specially successfully the method is applied to emeralds. The produced method also is used for analysis of the nature of painting of minerals
The Optical spectroscopy (the infra-red, visible and ultra-violet ranges) is applied to analysis of makeup of jewels and their painting
Luminescent spectrum-photometry (with various means of excitation of a cold light) serves for analysis of the nature of painting and allows to distinguish natural painting of jewels from syntheticly targeted
X-ray crystal analysis (monocrystal) allows to spot frame of crystalline material and allocation in frame of various additions
The high-res Electron microscopy serves for analysis of frame of material at microlevel. Now the permission about 1 angstrom (10^-8sm) is attained.