Encyclopedia of Global Resources part 35 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. . | 310 Diatomite Global Resources other elements although exact proportions vary. Purified diatomite is essentially silica SiO2 with an average molecular mass of . Diatomite has a melting point of 1 710 Celsius and a density of grams per cubic centimeter. Heating it to high temperatures forms cr ystalline silica. Diatomite is usually white if pure buff gray and rarely black. In situ it is generally found as a soft sedimentary rock or as powder. Raw diatomite is typically processed by a series of crushing drying sizereduction and calcining procedures to produce different grades of diatomite for different specialized applications. Description Distribution and Forms Diatomite is a soft chalklike fine-grained sedimentary rock composed primarily of the fossilized silica shells of microscopic algae called diatoms. It is finely porous is low in density and has low thermal conductivity. Diatom frustules are composed of two symmetrical silica valves which can be elaborately ornamented with tiny holes and protrusions. These tiny holes are what make diatoms an ideal material for filtration. The word diatom comes from Greek diatomos meaning cut in half because of the two valves. Diatoms live in a wide range of moist environments although most abundantly in marine oceanic and lacustrine freshwater environments. Three main types of diatomite deposits are recognized in the United States marine rocks near continental margins lacustrine rocks formed in ancient lakes or marshes and sedimentary rocks in modern lakes marshes and bogs. Another commonly used term for diatomite diatomaceous earth more properly refers to unconsolidated or less lithified forms of diatomite. One of the most important marine diatomite deposits is near Lompoc California reported to be the world s largest producing district by volume. Economically important lacustrine deposits in the United States are found in Nevada Oregon Washington and eastern California. In 2007 the United States produced 33 percent .
