TAILIEUCHUNG - Encyclopedia of Global Resources part 107

Encyclopedia of Global Resources part 107 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 988 Quartz Global Resources Quartz crystals are used in electronics. United States Department of Agriculture quartz crystals have been mined in Brazil and smaller crystals are found in the United States for example in Arkansas and New York State the Herkimer diamond deposits . However Arkansas mining of lascas nonelectronic-grade quartz that is used largely as feedstock to culture synthesize high-grade quartz cr ystals for use in electronic and other applica-tions ended in 1997 and cultured quartz crystals are now produced primarily in Asia. Primary Uses Cultured quartz crystals are used mainly in electronics. Lumbered natural quartz crystals cost twice as much per kilogram. The United States has about 7 000 kilograms of natural quartz stockpiles the larger of these can be used to seed the culturing process. Secondary uses are found in the gemstone industry. Technical Definition Quartz is sparingly soluble in water 6 parts per million and exists in solution as silicic acid formula H4SiO4 . Animals and plants take up the silicic acid which can be incorporated in tissues. Description Distribution and Forms A striking example of quartz is the gradual petrification of trees which occurs as the silica redeposits in the wood. Grasses such as bullrushes have considerable silica content and were chewed as primitive toothbrushes by early settlers in the United States. Cattle feeding on grass can develop silica deposits in the urinar y tract that may be life-threatening. Amorphous silica is also found in sponges sea cucumbers rice hulls bamboo and palm fronds. Diatoms build their exoskeletons of silica and after their death an adsorbent mineral called diatomaceous earth kieselguhr remains. Cr ystalline quartz occurs rarely in the biosphere but quartz cr ystals 100 nanometers in size have been found in the organism Chlorochytridion tuberculatum. Solid quartz is not particularly toxic when swallowed and the silica content of foods is easily tolerated but quartz dust arising .

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