Marble.

Marble - crystal-grained metamorphic carbonate rock, the product recrystallized limestone, at least - dolomite. Due to the close coupling of calcite grains each breed is well polished. In engineering and construction marble call any carbonate rocks, giving in satisfactorily polished - limestone, dolomite or marble. Metamorphism of pure limestone leads to the formation of marble, since the only possible change of calcite at high pressures and temperatures - its recrystallization. At least partial recrystallization of calcite can occur without the participation of dynamic metamorphism, and in some ancient limestone strata have been turned into marble without affecting diastrophism.

Marble composition during metamorphism does not change. Original carbonate rocks - or limestone or dolomite. Accordingly marble consists of calcite or dolomite or both minerals. However, if the original rock contained as impurities in the form of quartz, silica or kaolin, is formed during metamorphism such characteristic lime silicate, as tremolite, pyroxene and phlogopite. Carbonaceous material, dispersed in the limestone may be converted to graphite (pure carbon).

Some varieties of marble - the fine-grained, coarse-grained others so that they are well visible cleavage rhombohedron of calcite grains on. Marble hardness 2.5 - 4, bulk density 2.63 - 2.92 g/cm3. Conventional lime marble rapidly boil, dissolving in dilute acids, but dolomitic marble boil only in powder form. Pure calcite marble - insulator, has excellent electrical insulating properties.

Marble coloring is light, but the presence of even a fraction of a percent of impurities - silicates, iron oxide and graphite - leads to painting rocks in different colors and shades, including yellow, brown, red, green, and even black, and there are colorful, colorful marbles.

Marble deposit. Marbles spread quite widely. The most popular are Italian marble. The famous white statuary marble is mined near Carrara in Tuscany. Is also famous yellow Parian marble from Greece - a favorite material of Greek sculptors. In the U.S., considerable thicknesses of marble occur in the eastern part of the country - in Appalachia and other areas. Marble mining is also in North Africa. Large deposits of dolomite marbles are in Natal (South Africa).

In Russia, the marble is mined in the Urals and the Far East, in Karelia, Altai, Krasnoyarsk Territory in Ukraine - in the Carpathians, Crimea, Donetsk region, in Georgia, Armenia, Uzbekistan and East Kazakhstan. Fine-grained white marble sculpture Malguzarskogo field in Uzbekistan, according to experts, the best of the famous Carrara.

Дата добавления: 2015-09-04