sand(redirected from sand enteritis)
Also found in: Dictionary, Thesaurus, Medical.
sand,rock material occurring in the form of loose, rounded or angular grains, varying in size from .06 mm to 2 mm in diameter, the particles being smaller than those of gravelgravel,
particles of rock, i.e., stones and pebbles, usually round in form and intermediate in size between sand grains and boulders. Gravel is composed of various kinds of rock, the most common constituent being the mineral quartz.
..... Click the link for more information. and larger than those of siltsilt,
predominantly quartz mineral particles that are between sand size and clay size, i.e., between 1-16 and 1-256 mm ( 1-406 – 1-6502 in.) in diameter. Silt, like clay and sand, is a product of the weathering and decomposition of preexisting rock.
..... Click the link for more information. or clayclay,
common name for a number of fine-grained, earthy materials that become plastic when wet. Chemically, clays are hydrous aluminum silicates, ordinarily containing impurities, e.g., potassium, sodium, calcium, magnesium, or iron, in small amounts.
..... Click the link for more information. . Sand is formed as a result of the weatheringweathering,
collective term for the processes by which rock at or near the earth's surface is disintegrated and decomposed by the action of atmospheric agents, water, and living things. Some of these processes are mechanical, e.g.
..... Click the link for more information. and decomposition of igneous, sedimentary, or metamorphic rocks. Its most abundant mineral constituent is silica, usually in the form of quartzquartz,
one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO2.
..... Click the link for more information. , and many deposits are composed almost exclusively of quartz grains. Many other minerals, however, are often present in small quantities, e.g., the amphiboles, the pyroxenes, olivine, glauconite, clay, the feldspars, the micas, iron compounds, zircon, garnet, tourmaline, titanite, corundum, and topaz. Some sands—e.g., coral sands, shell sands, and foraminiferal sands—are organic in origin. Sand grains may be rounded or more or less angular, and differences in shape and size account chiefly for differences in such important properties as porosity (proportion of interstices to the total mass), permeability to gases and liquids, and viscosity, or resistance to flow. Permeability and viscosity are also affected by the proportion of clayey matter present. The chief agents in accumulating sands into deposits are winds, rivers, waves, and glaciers; sand deposits are classified according to origin as fluviatile, lacustrine, glacial, marine, and eolian. The most extensive superficial deposits are seen in the desertdesert,
arid region, usually partly covered by sand, having scanty vegetation or sometimes almost none, and capable of supporting only a limited and specially adapted animal population.
..... Click the link for more information. and on beaches. The surface of a sand deposit may be level or very gently sloping, or the sand may be gathered by wind action into ridges called dunes. Sandstonesandstone,
sedimentary rock 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
..... Click the link for more information. and quartzitequartzite,
usually metamorphic rock composed of firmly cemented quartz grains. Most often it is white, light gray, yellowish, or light brown, but is sometimes colored blue, green, purple, or black by included minerals. It results from the metamorphism of pure quartz sandstone.
..... Click the link for more information. rocks are indurated masses of sand, and sand deposits are sometimes formed by the weathering of sandstone and quartzite formations. Sand is used extensively in the manufacture of bricks, mortar, cement, concrete, plasters, paving materials, and refractory materials. It is also used in the metallurgical industry, in the filtration of water, in pottery making, in glassmaking, in the manufacture of explosives, and as an abrasive. Other industrial uses are numerous. Although soils entirely composed of sand are too dry and too lacking in nourishment for the growth of plants, a soil that is to some extent sandy (a "light" soil) is favorable to certain types of agriculture and horticulture, as it permits the free movement of air in the soil, offers less resistance than a clay soil to growing roots, improves drainage, and increases ease of cultivation. Sand to which nutrient solutions have been added is often used in soilless gardening.
small fragments of loose sedimentary rock or contemporary sediment. Sand consists of round and angular grains of various minerals and rock fragments ranging from 0.1 to 1 mm (from 0.05 to 2 mm or larger, according to other classifications). It also has admixtures of silt (aleurite) and clay particles.
Sand may be designated by its origin as river, lake, sea, fluvioglacial, or eolian sand. In terms of mineralogical composition the most common sands are quartz, glauconite-quartz, feldspar-quartz, and mica sands. Sand may contain valuable minerals— gold, platinum, diamonds, sapphires, rubies, zircon, rutile, sphene, and ilmenite—some of which are extracted. Both natural sand and man-made sand, produced by crushing rock, are used in construction and in the building-materials industry. Quartz sand is used as a raw material in making glass, as a component in manufacturing porcelain, earthenware, and construction ceramics, and as material for making casting molds. The quality of sand is determined by the size of its grains, its mineralogical composition, and the amount of impurities.
Sorted sand must have a strictly regulated grain composition. Natural sand is usually supplied in two grades: large (5–0.63 and 5–1.25 mm) and small (1.25–0.14 and 0.63–0.14 mm). Impurities may not exceed 2 percent. There are two grades of crushed sand, 800 and 400, depending on the strength of the original rock.
REFERENCESFadeev, P. I. Peski SSSR, part 1. Moscow, 1951.
Trebovaniia promyshlennosti k kachestvu mineral’nogo syr’ia, 2nd ed., issues 2, 29, 74. Moscow, 1959–63.
Grauvakki. Moscow, 1972.
What does it mean when you dream about sand?
A dream about sand might relate to pleasant memories of being at the beach. Alternatively, sand can represent time—as in “the sands of time”—or the insecurity of building one’s house in the sand. Sand is also associated with deserts and the lack of nourishing water. (See also Beach, Desert).