Mineralogy. Classification of minerals.

To assort minerals it is possible on a number of signs. It is possible to ooze minerals on a leading or characteristic device, viewing, for example, the minerals containing copper, lead etc. Exist genetic classifications in which ooze minerals on their origin, for example, minerals magmatic, pegmatitic, skarn etc. All these classifications are not satisfactory for some reasons, but can be used as an additional help material.

The most widespread is chemical classification of minerals. In a bottom of eduction of groups in this classification the chemical principle is figured. To assort minerals it is necessary by a chemical principle (on types of chemical combinations, on character of a chemical bond) with the binding account of structural features of minerals.

First of all in a kingdom of minerals it is possible to distinguish the elemental substances and linkings. Among the elemental substances we will view one class of the minerals meeting in the form of free of elements, - native devices.

Among linkings to a chemical sign (leading anions) following types are oozed.

I type. Sulphurous linkings or sulphides. These are linkings of metals with sulphur or analogues of sulphur - arsenic, antimony, tellurium, selenium.

II type. Haloid linkings or halides. Minerals concerning here represent linkings with halogens - fluorine, chlorine and is much more rare bromine and iodine.

III type. Oxygen linkings among which it is possible to ooze oxides - linkings of metals with oxygen and oxygen salts - linkings of metals with complex oxygen anions. The last extremely widespread in the nature, they are the pivotal minerals composing earth crust.

Native devices. In a native state in the nature are known about 40 chemical elements, but the majority of them meets very seldom.

The finding of elements in a native view is related to a structure of their atoms having inconvertible electronic shells. Chemically inertial naturally devices are termed as the noble; the native state for them is the most typical. Gold Au, argentum Ag, platinum Pt and devices of group of platinum concern them. Very often in a native state there is carbon C, sulphur S and copper Cu.

Less often there are so-called semimetals: arsenic As, antimony Sb, bismuth Bi. Such minerals as iron Fe, lead Pb, tin Sn, mercury Hg, meet as native extremely seldom and their finding represents only scientific interest. Some devices (chrome, aluminium) do not meet at all in a native view.

Sulphides. Minerals sulphurous and similar to them total more than 200 views, but their blanket content in earth crust is insignificant and does not exceed 0.15 %.

From the chemical point of view they are derivatives of hydrogen sulphide H2S in the core. In some rare minerals a sulphur place occupy Se and Te. By analogy to sulphides also ooze arsenides and antimonides. In all these linkings isomorphic displacements of one of elements are widely developed by others.

Disulfides and iron sulphides on which share it is necessary about all 4/5 sulphides have the greatest distribution. Customary sulphides are sulphides of copper, lead, zinc, argentum, antimony etc. In the form of isomorphic impurities in a composition of sulphides variety of the rare and diffused of elements, not forming self-maintained minerals rare and diffused of elements enters.

Sulphides for small exceptions have metal brilliance, major density and low hardness. There are they in the form of crystals, druses, more often - in the form of continuous granular masses and phenocrysts.

Origin of sulphides mainly hydrothermal, and also magmatic, skarn and for some exogenic - sedimentary.

At acidification sulphides decay and easily transfer in various secondary minerals: carbonates, sulphates, oxides and silicates, inconvertible in the superficial requirements.

Sulphides have major practical value are the major ores of lead, zinc, copper, argentum, nickel and other metals.

By a structural principle among sulphides it is possible to ooze sulphides coordination, chained, laminated and other structures. So, for example, sulphides can be assorted, oozing structural motives: coordination, island, chained, laminated.

Oxides - linkings of elements with oxygen, in hydrooxides there is also a water. In earth crust on a share of oxides and hydrooxides it is necessary about 17 %, from them on an earth silicon share (SiO2) about 12.5 %.

The most widespread minerals of this group are oxides of silicon, aluminium, iron, manganese and the titan.

In crystalline structures of minerals of a class of oxides cations of metals are in an environment of anions of oxygen (in oxides) or hydroxyl (in hydrooxides). Among oxides it is possible to ooze simple oxides in which relations between cations and anions change in limits from 2:1 to 1:2 (R2O, R2O3, RO2) and the difficult oxides for which double linkings of type RO*R2O3 are characteristic.

The origin of minerals of a class of oxides various - magmatic, pegmatitic, hydrothermal, but the majority of oxides was formed as a result of exogenic processes in the upper stratums of a lithosphere. Many endogenic minerals at airing collapse and transfer in oxides and hydrooxides.

Physical properties of oxides are various: for the majority of them high hardness is characteristic. Minerals of a class of oxides have major practical value.

Carbonates and sulphates. Carbonates - numerous group of minerals which have a wide circulation. In the structural relation all carbonates concern one basic type - anions [CO3] 2 represent the isolated radicals in the form of flat delta circuits.

The majority of carbonates anhydrous simple linkings, mainly Ca, Mg and Fe with a complex anion [CO3] 2. The difficult carbonates containing additive anions (OH) are less spread - F - and Cl-. Among the most widespread anhydrous carbonates distinguish carbonates of trigonal and trimetric syngonies.

Carbonates usually have light colouring: white, pink, grey etc., an exception the carbonates of copper having green or dark blue colouring represent. Hardness of carbonates nearby 3-4; the density is insignificant, except for carbonates Zn, Pb and Ba.

The important diagnostic sign is activity on carbonates of acids (HCl and HNO3) from which they to some extent boil with carbon dioxide eduction.

By origin carbonates sedimentary (biochemical or chemical precipitates) or sedimentary - metamorphic minerals; the superficial, characteristic acidifications for a band and sometimes low-temperature hydrothermal carbonates are oozed also.

Sulphates - salts of sulfuric acid. They have light colouring, the small hardness, many of them are soluble in water.

The great bulk of sulphates has a sedimentary origin are chemical sea and lake precipitates. Many sulphates are minerals of a band of acidification, sulphates and as yields of volcanic activity are known.

Distinguish sulphates anhydrous, water and difficult, containing except blanket for all an anionic complex [SO4] 2 also additive anions (IT)-.