But once that clam shell undergoes burial, diagenesis, or other geological processes, then the calcite is considered a mineral. Because of these discrepancies, the International Mineralogical Association in 1985 amended the definition to: “A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes.” This means that the calcite in the shell of a clam is not considered a mineral. Calcite is quite often formed by organic processes, but is considered a mineral because it is widely found and geologically important. Both are considered minerals because they were classified before the room-temperature rule was accepted as part of the definition. For example, water and mercury are liquid at room temperature. Some natural substances technically should not be considered minerals, but are included by exception. In geology, the classic definition of a mineral is: 1) naturally occurring, 2) inorganic, 3) solid at room temperature, 4) regular crystal structure, and 5) defined chemical composition. The term “minerals” as used in nutrition labels and pharmaceutical products is not the same as a mineral in a geological sense.
Describe the basic structure of the atom.The largest crystal found here is 39 feet (12 meters) and 55 tones.Īt the end of this chapter, students should be able to: These selenite (gypsum) crystals, found in The Cave of the Crystals in Naica, Mexico, has some of the largest minerals ever found. Water should not be used on burning magnesium or on magnesium fires.Announcement: Chapter quizzes are not working as of summer 2023. Handlingīecause serious fires can occur, great care should be taken in handling magnesium metal, especially when finely divided. The adult daily nutritional requirement, which is affected by various factors include weight and size, is about 300 mg/day. Chlorophylls are magnesium-centered perphyrins.
Organic magnesium is important in both plant and animal life. Dead-burned magnesite is employed for refractory purposes such as brick and liners in furnaces and converters. The hydroxide (milk of magnesia), chloride, sulfate (Epsom salts), and citrate are used in medicine. It is also used as a reducing agent in the production of pure uranium and other metals from their salts. Magnesium is used in producing nodular graphite in cast iron, and is used as an additive to conventional propellants. The metal improves the mechanical, fabrication, and welding characteristics of aluminum when used as an alloying agent. It is one third lighter than aluminum, and in alloys is essential for airplane and missile construction. Uses include flashlight photography, flares, and pyrotechnics, including incendiary bombs. It tarnishes slightly in air, and finely divided magnesium readily ignites upon heating in air and burns with a dazzling white flame. Magnesium is a light, silvery-white, and fairly tough metal. by electrolysis of fused magnesium chloride derived from brines, wells, and sea water. The metal is now principally obtained in the U.S. It does not occur uncombined, but is found in large deposits in the form of magnesite, dolomite, and other minerals.
Magnesium is the eighth most abundant element in the earth's crust. Davy isolated it in 1808 and Bussy prepared it in coherent form in 1831. Black recognized magnesium as an element in 1755. Compounds of magnesium have long been known. Because they are light and strong, magnesium alloys are often used for tire rims.įrom Magnesia, district in Thessaly.
0 kommentar(er)
