Diament

Diament belongs to the most valued gemstones. The name of the diamond comes from the Greek word adamas - invincible, what is related to its properties, primarily with hardness, the greatest of all minerals. Another distinctive feature of a diamond is its particularly strong luster, called diamond shine.

Diamonds are not only used as gemstones; much of the diamonds excavated is used in industry. In view of the high price of transparent gemstones, the value of their annual production exceeds that of industrial diamonds.

W 1974 r. mined in the world 44 522 thousand. carats of diamonds, of which were used for industrial purposes 32 210 thousand. kr (about 72%). The industrial use of natural diamonds has recently decreased due to the development of the production of synthetic diamonds. W 1974 r. produced them 77 100 thousand. kr; however, their grains are smaller than those of natural diamonds.

Chemically, diamond is pure carbon - C.. Traces of other elements found more than once in diamonds come from the most common impurities in the form of mineral inclusions. There are hardly any diamonds, which would not contain any tiny infixes; even the purest, most valued, their presence is found at microscopic examination.

A diamond does not undergo chemical changes and transformations; it is very resistant to chemicals. It does not dissolve in strong acids (sulfur, nitrogen or hydrofluoric), nor in the rules (sodium or potassium hydroxide). It was only stated, that it is oxidized by the action of nitrate or a mixture of potassium dichromate and sulfuric acid.

The diamond is burnt in the flame of the blower, changing to carbon dioxide CO2; and the heated diamond powder burns in air.

In an oxygen atmosphere, diamond burns at a temperature of 720 ° C; in air, combustion takes place at about 850 ° C. If the combustion process is interrupted by removing the heat source, can be observed, that the edges and corners of the stone are rounded, and shiny surfaces become dull and milky. With the help of a magnifying glass, you can see the presence of fine triangular grooves, being figures of diamond etching. Such superficial damage to the diamond can arise from careless heating when soldering the diamond holder. If it is not too big; they can be removed by polishing the sides.

Due to the unusual properties of the diamond, some researchers have assumed, that it consists of some special element, which was called diamond earth. The structure of the diamond was clearly defined only in the first half of the 19th century.

Compared to graphite, which is a type of carbon that is persistent in the earth's crust, the diamond is an unstable variety, transforms into graphite when heated in the absence of air. This transition at low pressures is unidirectional and attempts to obtain diamonds from graphite have failed.

The diamond crystallizes in a regular pattern, most often forming octahedrons. Rhombic dodecahedrons are less common, cubes and tetrahedra, as well as other characters. The form richest in walls is the forty-octahedron.

Diamond crystals are rarely limited by flat faces and straight edges. The faces of the crystals are usually rounded and create uneven surfaces. These surfaces intersect, creating arcs of variable curvature. On many faces of the crystals there are protrusions, depressions and striations, sometimes in the form of a mesh. The most common are octahedrons with slightly rounded walls; sometimes they take a shape similar to a sphere. Also, the second cubic diamond crystals are often rounded. There are also deformed crystals, which have lost their original shape and the crystals as if nibbled. These characteristic deformations of diamond crystals are related to their growth conditions, as well as with their subsequent dissolution.

Twin adhesions of diamond crystals are not uncommon. They are formed by the adhesion of two single crystals; the fusion plane is usually the octahedron plane. In addition to twins, multiple twins are common. Coated diamond crystals can sometimes be difficult to grind.

Irregular, compact adhesions are often found, fine crystalline clusters. They are called bort. The radiant aggregates of diamond crystals are known as ballas. Circular clusters, ziarniste, gray and of various sizes, up to the size of the egg, coke-like in appearance, are called carbonado (carbonado). They are found mainly in Brazil. Due to their opacity and high abrasion resistance, these varieties are used in industry.

Construction of a diamond. A diamond's spatial lattice can be represented by two regular faces with centered faces, one of which in relation to the other is shifted towards the main diagonal of the cube. The internal structure of diamond is different from that of graphite, which has the same chemical composition. This different internal structure explains the property differences, especially different hardness - a diamond is an example of the hardest body, and graphite - the softest. By comparing the distribution of carbon atoms in diamond and graphite, clear differences can be seen. The bonds between the individual carbon atoms in the diamond lattice belong to the atomic bonds. Each of the carbon atoms, which are more tightly packed in the diamond crystal than in the graphite crystal, it is surrounded by four other carbon atoms, at equal distances; the angle between the bond directions is 109 ° 28′. In graphite, the atoms are arranged in layers, as a result, the bond between the atoms is much weaker.

One of the characteristics of graphite is cleavage parallel to the planes of the densest arrangement of carbon atoms, according to these planes, the bonds between the carbon atoms are stronger than in directions perpendicular to them. In a diamond, the carbon atoms are arranged more densely in the planes of the octahedron, which explains his cleavage.