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Minerals

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Earth crust consists basically of the substances named minerals - from rare and extremely valuable diamonds to various ores from which receive metals for our daily needs.

Minerals have played the major role in development of the person and creation of civilisations. In the Stone Age people used silicon instruments of labour. About 10 000 years ago person has mastered a way of reception of copper from ore, and with the bronze invention (a copper and tin alloy) the new century - bronze has begun. From the Iron Age beginning, 3300 years ago, the person mastered all new and new ways of use of the minerals extracted from earth crust. The modern industry still depends on mineral resources of the Earth. Scientists total about 3000 kinds of minerals, but only 100 of them enough widespread. Minerals concern the inorganic (lifeless) world. More often they are firm substances. The exception makes mercury.

Organic and inorganic substances

Many name minerals everything that extract from the earth. They carry to this category also fossil fuel, for example, coal. However, mineralogi - people who professionally study minerals, - consider that coal, oil and natural gas - organic substances as were formed of the rests once live plants and animals that is why minerals are not.

At minerals a certain chemical compound. They always are homogeneous, in other words, all parts of a mineral are identical. It they differ from the rocks including of some minerals.

Minerals consist of chemical elements, i.e. Substances which already cannot be spread out to other substances a chemical way. From 107 elements known to a science 90 meet in a natural kind in earth crust. Some, them name native elements, stay in earth crust in pure or nearly so a pure kind. There are 22 native elements, among them - gold, silver and diamonds (one of carbon forms).


Earth crust

Two elements, oxygen and silicon, make 74% of weight of earth crust. Aluminium, iron, calcium, sodium, kaly and magnesium - 24,27 more%. All together they form almost 99% of earth crust.

The Most widespread minerals are silicates, an oxygen and silicon chemical compound, is frequent with an impurity of one or more of other six elements. Such silicates, as quartz, mica and field spars prevail. All three in different proportions are the basic components of different types of a granite. Quartz, erodirovannyj from a granite, collects at coast and forms sandy beaches.


Definition of minerals

Often meeting minerals, such as field spars, quartz and mica, are called porodoobrazujushchimi. It distinguishes them from minerals which find only in small amounts. Kaltsit - one more porodoobrazujushchy a mineral. It forms calcareous breeds.

Definition of minerals In the nature exists so many minerals that mineralogam it was necessary to develop the whole system of their definition based on physical and chemical properties. Sometimes to distinguish a mineral very simple properties help, for example, colour or hardness, and at times for this purpose are required difficult tests in vitro with application of reagents.

Some minerals, such as (dark blue) and malachite (green), it is possible to distinguish lazurite on colour. But colour is often deceptive, because at many minerals it widely enough varies. Distinctions in colour depend on impurity, temperature, illumination, radiation and erosion.


Line of a mineral and hardness

If poskresti the mineral, at us turns out a powder named line of a mineral. Line is the important prominent feature, it sometimes differs from colour of a mineral in the sample and is usually constant for the same mineral.

Still minerals differ on the hardness estimated on a scale of Moosa (by name Austrian mineraloga) from 1 to 10. The soft mineral talc on it corresponds 1, and diamond, firmest of natural materials, - 10.


Relative density

Relative density, or density, is a parity between weight of substance and an identical quantity of water. If we accept relative density of water for 1 at the majority of minerals it varies from 2,2 to 3,2. At some minerals very high or very low relative density. For example, at graphite it is equal 1,9, and at gold - from 15 to 20 depending on cleanliness.

One more indicator for definition of minerals is klivazh, i.e. How the mineral breaks up to parts at blow. It is possible to receive the information on a mineral and having brought it to light. Transparent minerals so easily pass light that through all of them it is visible. Translucent too pass light, but through them already it is visible nothing. Opaque minerals at all do not pass light, and, on the contrary, absorb it or reflect. Often minerals have a metal or iridescent shine. For example, at galena (lead ore) - metal shine, it shines almost as metal, and at the majority of silicates - steklovidnyj, they remind brilliant glass. There are also other kinds of shine - adamantovyj (as at diamond), pearl, silky (or satiny), earthy (dim). Some minerals can have some kinds of shine. So, shine kaltsitov varies from steklovidnogo to the earthy.

Many minerals have specific properties on which they are easy for learning. For example, skorodit and a native element arsenic at heating smell as garlic, and talc - soap to the touch.

Some minerals fluoresce (are shone or change colour) in ultra-violet or X-rays. Others elektricheski are charged at heating or under pressure.

And there are minerals, to distinguish which it is possible only by means of special tests in laboratory. One are dissolved only in hot acids, and in cold - are not present, others - only in concentrated, but not in dissolved.


Crystals

Minerals have certain structure and the chemical formula. The chemical formula galita (stone salt) NaCl. It means that galit - a sodium chemical compound (Na) and chlorine (Сl).

As at each mineral the certain and constant structure, atoms of its elements build a correct three-dimensional lattice of structure specific to it. These crystal lattices are the geometrical figures which flat sides are symmetrized. If you leave for some time in flat ware a little salty water, it will evaporate, and salt crystals are at the bottom formed. In magnifying glass it is visible that they represent correct cubes.

There are seven basic kristallograficheskih, or isometric, the systems named singonijami. Diamond, for example, belongs to cubic system, a ruby - to geksagonalnoj, turquoise - to triklinnoj. Each system can be described according to specificity of its symmetry - property which at rotation of a crystal round an axis allows it to appear in an identical kind two or more times for one complete revolution. The crystal can be defined by quantity of axes of symmetry.


Precious minerals

Precious minerals in the Stone Age people did ornaments of gold, in a bronze age - from silver. Today at the disposal of jewellers set of minerals. The most expensive jewels are a diamond (especially colourless), and also emerald, a ruby and sapphire which are appreciated first of all colour. These stones so expensive that measure their weight in carats. One carat is equal to 200 milligrammes.

Diamonds are formed under huge pressure in structures of magmatic breed in the form of a pipe, kimberlitah. They arise deeply in a cloak of the Earth. Diamond is a version of chemically pure coal and on a chemical compound does not differ from an ordinary soft mineral of the graphite familiar to us on pencils. Diamond appreciate hardness and the shine got at a facet and polishing. The reason of such difference of diamond from graphite that they have different internal structure. Ability of substance to exist in two and more forms at an identical chemical compound is called as polymorphism.

So, for example, the emerald is a rare version of beryl. The most beautiful copies find in Colombia (South America). And the most known rubies in the world (a version of a firm mineral of corundum) - in Myanma (the former Burma). Fine sapphires (blue corundum) extract on Sri Lanka and in Thailand.