Magnesite

About: Magnesite is a research topic. Over the lifetime, 2571 publications have been published within this topic receiving 35579 citations. The topic is also known as: giobertite & carbonate magnesium.

Carbonate identification and genesis as revealed by staining

Abstract: Carbonate minerals are stained over a set period of time with alizarin red-S and potassium ferricyanide only if they will react with dilute hydrochloric acid solution, with which the stain is prepared. The rates of solution of carbonates in the acid control the intensity of color development. For calcite, the rate of solution varies with the optic orientation of the section. The speed of carbonate solution is changed if the acid concentration is altered, but only at concentrations of about 0.1 N is the optic orientation of calcite differentiated by the stain. Etching reduces thin section thickness and clarifies rock texture. Staining with alizarin red-S differentiates carbonate minerals into two groups. Aragonite, calcite, witherite, and cerussite, which dissolve rapidly in dilute hydrochloric acid, are stained, while dolomite, siderite, magnesite, and rhodochosite, which react much more slowly with the acid, remain unstained. The distribution of ferrous iron, as distinguished by staining with potassium ferricyanide, has proved to be highly significant in the genesis of cements. Ferrous iron can be introduced at any one stage in cementation, or repeatedly, forming zoned patterns. The paragenesis of zoned ferroan cements can be reconstructed after staining. Solution of the more soluble original constituents can sometimes be dated in relation to cementation. Ferroan calcite can be secondary in origin and is usually associated with replacement minerals.

Magnesium chemistry and biochemistry

Abstract: Magnesium apparently derives its name from Magnesia, a district in the Volos area of Thessaly in northeastern Greece. It was used to refer to any of several minerals ranging from magnesite (magnesium carbonate or ‘magnesia alba’) to magnetite (manganese dioxide or ‘magnesia nigra’) and also magnesia stone (talc or soapstone), a magnesium silicate. However, there are also two ancient towns in Asia Minor named Magnesia from the Greek word magnes used to refer to the magnetic iron ore discovered in this area. Magnesia could have been derived from magnes but used for another mineral in a different place, just as magnesia in Greece referred to several minerals. Magnesium metal was first prepared by Sir Humphrey Davy around 1810 by making the amalgam of magnesium with mercury and then distilling off the mercury electrolytically (Treneer 1963). Davy named the new metal magnium and the word magnesium was initially used for manganese, derived from the mineral ‘magnesia nigra’. The pure metal is highly reactive and all magnesium in the biosphere is either the free cation Mg2+ in aqueous solutions or some salt or mineral form. There are several common mineral forms of magnesium in the environment. Dolomite [MgCa(CO3)2] derives its name from the Dolomite range in the Italian Alps. The story of the recognition of dolomite and various controversies that have ranged and still range around this mineral makes interesting reading for the historian of science (Hacking 1999; McKenzie 1991). Epsomite (MgSO4 · 7H2O) derives its name from the Epsom district in England, originally south of London but now incorporated into greater London. Epsom water originally came from a spring that arose on the common of Epsom village. Epsomite proved to be a major constituent of the waters. Application proved efficacious in healing of external ulcers, and the water became a destination for the sick. Until the first decade of the 18th century, Epsom was a well-known spa with many visitors partaking of the waters internally, where it acts as a purgative (Sakula 1984). Other minerals containing large amounts of magnesium are olivine (Mg2SiO4), magnesium calcite (MgSO4) and chrysolite [asbestos, Mg3Si2O5(OH)4], as well as garnet and spinel, which also contain aluminum with the magnesium.

Mineral Carbonation of CO2

Abstract: A survey of the global carbon reservoirs suggests that the most stable, long-term storage mechanism for atmospheric CO2 is the formation of carbonate minerals such as calcite, dolomite and magnesite. The feasibility is demonstrated by the proportion of terrestrial carbon bound in these minerals: at least 40,000 times more carbon is present in carbonate rocks than in the atmosphere. Atmospheric carbon can be transformed into carbonate minerals either ex situ, as part of an industrial process, or in situ, by injection into geological formations where the elements required for carbonate-mineral formation are present. Many challenges in mineral carbonation remain to be resolved. They include overcoming the slow kinetics of mineral-fluid reactions, dealing with the large volume of source material required and reducing the energy needed to hasten the carbonation process. To address these challenges, several pilot studies have been launched, including the CarbFix program in Iceland. The aim of CarbFix is to inject CO2 into permeable basaltic rocks in an attempt to form carbonate minerals directly through a coupled dissolution-precipitation process.