Metal extraction from ores occurs in many different ways involving physical, chemical and electrical means. Even ores of the same metal sometimes require different methods of separation depending on the concentration of the metal and its chemical composition within the ore.
Ores are naturally occurring sources of metal. From a practical standpoint, ores include materials from which extracting the metal is economically feasible. Aluminum is the most common metal in the Earth's crust. However, all sources of aluminum are not equal. Due to the high cost of refining and the relatively low value of the metal, extraction is limited to bauxite, an aluminum ore containing 50 to 70 percent of aluminum oxide.
Copper ores generally contain sulfides or oxides and copper in the 0.5 to 2.0 percent range. Because of the greater value of copper metal, refining ores at these levels is profitable. Refiners crush copper sulfide ores mechanically and use froth floatation to bring copper-containing particles to the surface of a water solution. The material is then heated to over 930 degrees Fahrenheit to burn off the sulfur and create 60 percent pure copper in a calcine mixture of copper oxides and sulfides. The calcine mixture is heated again to over 2100 degrees Fahrenheit with a flux. At this temperature, slag floats to the surface and workers skim it away. Refiners oxidize the liquid copper to remove iron and remaining sulfur components, resulting in 97 percent pure copper. Electroplating is the final step in producing 99.99 percent pure copper. Processing copper oxides requires a completely different process, involving leaching.Learn More
Hurricane Andrew began as a tropical wave that crossed the west coast of Africa into the tropical North Atlantic on August 14, 1992. Two days later, after it passed just south of the Cape Verde islands, the wave became a tropical depression. Tropical Storm Andrew formed August 17 and became a hurricane three days later due to vertical wind shear. The hurricane caused 23 deaths in the United States.Full Answer >
Basalt is crushed and used to pave roads. It is also used to provide ballast for railroads and as a building stone. It is used in sculpture and to make basalt fiber and rock wool. Basalt can also be cut into flags and polished and used as flooring material.Full Answer >
According to About.com, agate forms from the deposition of silica in aqueous solution at low water depths and relatively low temperatures. It is a form of chalcedony mineral, which is a mass of quartz composed of microscopic crystals. Its porous nature, relative to other forms of quartz, allows it to develop impurities that give it a variety of colors and patterns, making it a popular stone for use in jewelry.Full Answer >
Marble is a metamorphic rock formed from limestone. Changes in the limestone's chemical properties due to external forces can result in the creation of marble.Full Answer >