Different kinds of rocks are used as building materials or decorative stones. Stones are commonly used in the construction of buildings, roads, and pathways, and in the making of rockeries in both public and private areas. In the case of rockeries, it is very important to create a replica of some natural environment. There is a natural relationship between a rock, its weathering and any related soils. Depending on the chemical composition of the rock, soils will have a more acid or basic character. The chemical character of soils, and climatic conditions, are reflected in the plant species that occur. Rockeries should reflect these relationships. Thus the kind of rocks used in their construction is extremely important. Moreover, it is not only chemistry but even the rock colors that should be considered. Rock color influences the colors of soils. The temperatures of soils depend on color too, particularly on sunny summer days. This it is not without significance if, for example, a plant which in its natural environment grows on white limestone is planted on black limestone. Roads, pathways, steps, the borders of pools, etc., are other important elements in many gardens and rockeries. All of these should also involve natural stone with a color corresponding to the character and color of their surroundings. Natural processes result in the decay of rocks in both the natural environment and in gardens and rockeries. In towns, decay is more pronounced because of the air pollution and the lack of proper ventilation. Decay processes (deterioration) caused by anthropogenic pollution facilitate the activity of micro organisms that can be very destructive for rocks. Hydrophobization, commonly applied to decorative stones in architecture, can be also applied in small garden-architecture in order to inhibit plant growth in those parts of rockeries which are intended should not be covered with plants - even where the rock would permit the easy migration of water.