SILICATES

 
This is the most numerous, and on structural and chemical structure – complex class. Minerals are  in weight up to 85% of the earth’s crust and rock constituent.
The basic structural unit of silicates – are silicon-oxygenic tetrahedron, with 4 free valence bonds, due to which there is a connection ions of other elements. Method of connection tetrahedrons determines the form of crystals of minerals constitute the basis for the division of silicates into the following subclasses:1) island, 2)ring, 3) chain, 4)tape, 5) leaf, 6) carcass.

Island silicates, according to a dense packing of ions possess with high hardness and rather high specific weight. Olivine and grenades-almandine are related to the island. Let’s consider olivine.
OLIVINE (peridotite) – the colour of the olive-green, bottle-green, doesn’t give features. Shine glass, transparent or translucent, break rough, grainy, imperfect cleavage. Hardness of 6.6-7, weight average. Occurs in the form of granular assemblies or individual grains in the breed.
Different green, high hardness. The origin of igneous rock. The basic mineral ultrabasic and the basic rocks.
Aggregates of more or less constant mineral composition and structure are called the rocks. In origin, they are divided into three groups: magmatic and sedimentary and metamorphic.

Magmatic rocks are formed by the solidification of the magma-hot-melt, infused in the upper zone of the earth’s crust from the deep subsurface area.
Depending on conditions of solidification of magma there are two groups of magmatic rocks-intrusive and effusive. According to chemical composition, which is largely determined by the content of silica, all magmatic rocks are divided into:
– ultrabasic;
– main;
-middle;
– sour.
Determinations of the names of magmatic rocks should be focused on their main characteristics.

This is first of all, the texture and structure of the breed. These characteristics give the opportunity to solve the question of the ownership of the breed to intrusive or effusive formations. Intrusive group relates to: granite and syenite, diorite, gabbro. Effusiveе group relates to: liparit, trachyte, andesite, basalt.
Magmatic and sedimentary rocks after their formation may remain without significant changes hundred thousands and millions of years. However, in the manifestation of tectonic movements and magmatism or under the weight of the overlying strata of rocks they change and converted to the new breed, which have received the name of metamorphic rocks. The main factors of fluids and gases released by magma during its implementation. Metamorphic rocks, as magmatic, are widely used in the construction business, for example, marble quartzrock.

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