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aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.
..... Click the link for more information. formed by the cementing together of grains of sand. The usual cementing material in sandstone is calcium carbonate, iron oxides, or silica, and the hardness of sandstone varies according to the character of the cementing material; quartz sandstones cemented with quartz are the hardest. Sandstones are commonly gray, buff, red, or brown although green and some other colors are also found. Green sandstones often contain, in addition to sand and glauconite, fossil shells and iron oxides; those that break apart easily are known as greensands and are sometimes used to replenish depleted potash in soils. Sandstones are widely used in construction and industry. Varieties of sandstone include arkose, which contains feldspar and resembles granitegranite,
coarse-grained igneous rock of even texture and light color, composed chiefly of quartz and feldspars. It usually contains small quantities of mica or hornblende, and minor accessory minerals may be present.
..... Click the link for more information. , and graywacke, a gray or sometimes greenish or black rock composed of quartz and fledspar with numerous fragments of other rocks, such as shale, slate, quartzite, granite, and basalt. Sandstone may be crushed to the form of loose sand grains, which can then be put to the same industrial uses as sand. See brownstonebrownstone,
red to brown variety of sandstone. Its unusual color is caused in some instances by the presence of red iron oxide which acts as a cement, binding the sand grains together.
..... Click the link for more information. .
a sedimentary rock composed of sand grains cemented by clay, carbonate, siliceous, or other material. Like sand, sandstones are divided into small-grain (0.1–0.25 mm), medium-grain (0.25–0.5 mm), and large-grain (0.5 mm) varieties according to the predominant particle size. They are also divided mineralogically into monomineral and polymineral quartz sandstones, arkosic sandstones, and graywackes.
The density of sandstone is 2,250–2,670 kg per cu m; its porosity is 0.69–6.70 percent, and its water absorption, 0.63–6.0 percent. Sandstone with siliceous and carbonate cementing material has the best physicomechanical properties, and sandstone with clay cement, the poorest. The refractoriness of sandstone also differs, with the greatest heat resistance (up to 1,700°C) characteristic for pure quartz sandstone with siliceous cement. Sandstone is used in construction as wall and facing material and in rubble work. It is also used to make gravel for road building and concrete-making. Quartz sandstone with a SiO2 content of more than 95 percent is used in the production of Dinas brick, as a flux in smelting copper and nickel, and in manufacturing glass.