Geology. Козлова Е.П. - 16 стр.

     2.3. Прочтите и переведите текст 1А

                          Minerals and Mineral Deposits

       Minerals that make up the rocks, are defined as inorganic substances which
occur naturally and have a definite chemical composition and physical properties.
The major properties which are used for identification purposes are: 1)color; 2)crystal
form; 3)cleavage; 4)specific gravity; 5)hardness; 6)luster.
        More than 2 000 minerals are known. Some are relatively simple compounds
of elements in the solid state, others are complex. Minerals of use to man can be
grouped into two broad categories :
    1) metals, such as aluminium, copper, gold, silver, iron, tin, platinum, chromium,
       nickel, lead, zink, etc;
    2) non-metals, such as diamond, salt, limestone, cement, sulphur, crydite,
       asbestos, etc.
       The term “mineral” is also applied for such organic substances as coal, oil and
natural gas.Minerals may be formed by four general processes, which may be
intimately related in nature :
    1) from a gas by sublimation ;
    2) from a liguid (agueous solution) ;
    3) from a liguid / molten rock or magma ;
    4) from a solid by metamorphism.
       Mineral deposits have been found both in rocks that lie beneath the oceans and
in rocks that form the continents. Mineral deposit are not uniformly distributed in the
earth’s crust. In certain regions unusual conditions caused the concentration of
elements far in excess of normal abundance. These regions are called mineralogenetic
provinces. Mineral deposits have different shapes, depending on how they were
deposited. The most common shape is tabular, with the mineral deposit lying as a
filling between more or less parallel layers of rocks. Mineral deposits are seldom
egually rich throughout.
       After their formation mineral deposits may be deformed by folding, faulting,
brecciation or weathering. Mineral deposits that are essentially as originally formed
are called primary deposits. Deposits that have been altered by weathering or other
superficial processes are secondary deposits. Every mineral deposit has limited
dimensions. All mineral deposits are exhaustible.

      2.4 Ответьте на следующие вопросы

1) What is mineral?
2)What are the major properties used for identification purposes?
3) How many minerals are known?
4)How can minerals be grouped?
5) What are the four general processes which form minerals?
6)Where are minerals concentrated?

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