Прочитайте текст и выполните задания
Marble: characteristics, uses and problems
1. Marble is an extremely hard, metamorphic stone composed of calcite (CaCO3). It is formed as a result of the recrystallization of limestone under the intense pressure and heat of geologic processes. The effect of this process is the creation of a stone with a very tight crystalline structure and small but definite porosity.
2. Because of its structure, marble can take a very high polish and is a very popular decorative stone for architectural and sculptural uses. The limited porosity of marble, especially polished marble, makes it less vulnerable to the leaching effects of water. Calcium carbonate, however, of which marble is composed, is highly susceptible to attack by acidic agents. Marble is readily dissolved by acids, even very dilute acids, however the actual results of acidic exposure will vary with the nature of the acid. For this reason, it is always important to determine the exact type of pollutants causing marble deterioration.
3. Marble has many decorative and structural uses. It is used for outdoor sculpture as well as for sculpture bases; in architecture it is used in exterior walls and veneers, flooring, decorative features, stairways and walkways. The way in which the stone is used may be a factor in limiting or controlling the severity of exposure. The use or function of the marble may also affect the feasibility of applying certain treatments, but type of use is not the primary factor in the major types of deterioration and damage to which marble is susceptible.
Основной идеей текста является …
Marble is composed of calcium carbonate which makes it hard, rigid, porous, easy polished and a quite demanding material.
It is well-known that deterioration of marble depends mostly on the type of its use, chemical composition, age and origin.
Marble is a result of recrystallization of limestone which was naturally subjected to high temperature and pressure.
Due to its exterior marble is popular for indoor and outdoor decorations, though it is vulnerable to some contaminants.
