Magnesite applications

Magnesium occurs in many igneous rocks and in dolomite. It is usually obtained from seawater (1300 mg kg-1) or from the minerals magnesite (MgCC>3) or carnallite (KCl-MgCl2-6H20). The metal is used in lightweight alloys, MgO is employed as a refractory material and as an adsorbent for water treatment, and other Mg compounds find applications in the pharmaceutical and chemical process industries. 

The applicability of scanning Auger spectroscopy to the analysis of carbonate mineral surface reactions was demonstrated by Mucci and Morse (1985), who carried out an investigation of Mg2+ adsorption on calcite, aragonite, magnesite, and dolomite surfaces from synthetic seawater at two saturation states. Results are summarized in Table 2.5. 

The first two methods are preferred in industrial applications. They are used for producing porous insulating materials of fireclay, silica, high-alumina materials, magnesite, stabilized zirconia etc. Their thermal conductivity is several times lower than that at a standard porosity (cf. Fig. 214). 

For steelmaking applications, the MgO should be as pure as possible with minimum pore content in fired ware. The chemical methods for enriching natural magnesite enable products containing even more than 98% MgO to be produced. The following processes have been devised (cf. Staroh, 1978) ... 

Dead-burned magnesia is used almost exclusively for refractory applications, primarily in brick and basic granular refractories. The essential qualities of dead-burned magnesite that make it suitable for refractory applications are that it has a very high melting point (2800°C), it does not oxidize, and it has excellent resistance to attack by iron oxide, alkalis, and... 

The Santa Fe Mine, located in west central Nevada, has utilized magnesite and brucite, mined from the nearby Gabbs magnesite deposit, as a chemical cap. These were placed on the tops and side slopes of the sulfidic mineral dumps before cover soil application. The chemical cap consisted of placement of 20 tons per acre, followed by 8-12 in. of cover soil. The magnesite and brucite provided an alkalinity of 1920 mg/kg of soil. 

The talc/magnesite variety of ores are derived from serpentinite hosts and are typically found in Vermont, Quebec, and Finland. This type of ore is macrocrystalline in nature and composed of approximately 45-65% talc by weight, with the remainder of the ore made up of magnesite (magnesium carbonate). In some low-cost applications, such as automotive underhood, these ores are coarsely ground and used as is. These ores are also frequently beneficiated to 93-99 wt% talc by flotation. Because talc is hydrophobic, it is easy to float with surfactants. The talc floats on an aqueous bubble, whereas the co-mineral impurities sink in the water phase. 

High-temperature The predominant industrial application of magnesium compounds is in the use of thermal insulation magnesite and dolomite in refractory bricks. Bricks of high-purity magnesia are (2%) exceptionally wear and temperature resistant, with high heat capacity and... 

Industrial applications. Raw magnesite is used for surface coatings, landscaping, ceramics, and as a fire retardant. 

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