Encyclopedia of Global Resources part 22 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. . | 180 Carbonate minerals Global Resources Na2CO3 2H2O hydromagnesite Mg5 CO3 4 OH 2 4H2O and artinite Mg2 CO3 OH 2-3H2O . The most abundant carbonate mineral is calcite CaCO3 which comprises limestone chalk travertine tufa sedimentary rocks and marble metamorphic rock . Most limestone forms in warm shallow seas far from sources of land-derived sediment. Chalk is made of the shells of microscopic floating organisms which once lived in the sea. Spring deposits are travertine or tufa and cave deposits stalactites and stalagmites are travertine. These deposits form from the evaporation of groundwater carr ying dissolved calcium carbonate. Marble is limestone which has been changed by heat and pressure. Malachite and azurite are associated with the oxidized portions of copper deposits and with copper veins through limestone deposits. Sodium carbonate minerals are present in association with dry salt lake deposits in some parts of the world. These include trona natron Na2CO3 10H2O thermonatrite NaCO3 H2O nahcolite NaHCO3 gaylussite CaCO3 Na2CO3 5H2O pirssonite CaCO3 NaaCO HaO and shortite 2CaCO3- Na2COs . History Calcite because of its abundance has a rich histor y. Because calcite can preserve fossil records its presence helps date cultural artifacts. Chalk has been used for writing for thousands of years. Obtaining Carbonate Minerals The most important use of calcite is in the production of cements and lime. When limestone is heated to about 900 Celsius it loses CO2 and is converted to quicklime or lime CaO . Mixed with sand quicklime forms mortar. When mixed with water it hardens or sets swelling and releasing heat. The most widely produced cement is portland cement used in concrete which is generally made from limestone and silica- and alumina-bearing material such as clay or shale. The raw materials are ground together and the mixture is heated in a kiln until it fuses into a clinker which is then crushed to a powder. Uses of Carbonate Minerals Lime CaO is also used .
