Magnesite is a magnesium carbonate mineral with MgCO3 as its chemical composition. It gets its name from the fact that it contains magnesium. Magnesite is formed when magnesium-rich rocks or carbonate rocks are altered by metamorphism or chemical weathering.
Magnesite is used to make magnesium oxide (MgO), which is used in the steel industry as a refractory material and as a raw material in the chemical industry. Magnesite is also used as a gem and lapidary stone in small quantities.
In Magnesite ore, the Magnesite is found as veins in ultramafic rocks, serpentinite, and other magnesium-rich rock forms, as well as as an alteration element, in both contact and regional metamorphic terrains. These magnesites are mostly cryptocrystalline and contain opal or chert as silica. Magnesite is also found as a secondary carbonate in the regolith above ultramafic rocks, as well as in soil and subsoil, where it is formed as a result of magnesium-bearing minerals being dissolved by carbon dioxide in groundwaters.
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The talc carbonate metasomatism of peridotite and other ultramafic rocks may result in the formation of magnesite. Magnesite is formed when olivine is carbonated in the presence of water and carbon dioxide at high temperatures and pressures, as in the greenschist facies.
Magnesite has been discovered in sedimentary rocks, caves, and soils. Its low-temperature formation is known to necessitate alternating periods of precipitation and dissolution.
Magnesite has been discovered in the meteorite ALH84001 as well as on Mars itself. Magnesite was discovered on Mars by using infrared spectroscopy from space. Mg-carbonates have been found near Jezero Crater and are thought to have formed in the lacustrine climate. The temperature at which these carbonates form is still a point of discussion. The magnesite from the Mars-derived ALH84001 meteorite has been attributed to low-temperature formation. The formation of magnesite at low temperatures may be essential for large-scale carbon sequestration.
The extraction of magnesite from peridotite is favoured by magnesium-rich olivine (forsterite). The synthesis of magnetite-magnesite-silica compositions is favoured by iron-rich olivine (fayalite).
Magnesite can also be found in skarn deposits and dolomitic limestones, where it is associated with wollastonite, periclase, and talc as a result of metasomatism.
Magnesite has been suggested as one of the main carbonate-bearing phases in Earth's mantle and as a potential carrier for deep carbon reservoirs due to its resistance to high temperatures and ability to withstand high pressure.
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Magnesite can be burned in the presence of charcoal to produce MgO, which is known as periclase in the form of a mineral, similar to how lime is made. Magnesite is burned in large amounts to produce magnesium oxide, a refractory material used as a lining in blast furnaces, kilns, and incinerators. Calcination temperatures determine the reactivity of resulting oxide products, and the terms "light burnt" and "dead burnt" refer to the product's surface area and resulting reactivity, which is usually measured by an industry metric called the iodine amount. The term "light burnt" refers to calcination that starts at 450°C and goes up to 900°C, resulting in a substance with a lot of surface area and reactivity. Over 900°C, the material loses its reactive crystalline structure and transforms into the chemically inert 'dead-burnt' substance, which is ideal for use in refractory materials including furnace linings.
Magnesite is also used as a binding agent in flooring. It is also used as a catalyst and filler in the manufacture of synthetic rubber, as well as the manufacture of magnesium chemicals and fertilisers.
Magnesite couples can be used for cupellation in fire assays because the magnesite cupel can withstand high temperatures.
Magnesite beads can be cut, drilled, and polished to make them suitable for jewellery making. Magnesite beads can be coloured in a wide range of vibrant colours, including a light blue hue that resembles turquoise.
The possibility of sequestering the greenhouse gas carbon dioxide in magnesite on a wide scale is being investigated. This research has focused on ophiolitic peridotites, where magnesite can be produced by enabling carbon dioxide to react with the rocks. In the case of ophiolites from Oman, some progress has been made. However, the main issue is that these artificial processes necessitate enough porosity-permeability for the fluids to flow, which is rarely the case in peridotites.
Magnesite is an excellent material for producing colourful, low-cost costume jewellery and art projects because of its low production costs and wide range of dyed colours. The disadvantage of using magnesite for jewellery is that it is less durable than other gem materials. Customers consider a material with a Mohs hardness of 3.5 to 5 in exchange for the low cost.
Tumbled stones, beads, and cabochons are all made from magnesite. White magnesite has a porous structure. It can be cut and will absorb dye reliably to create almost any colour. Magnesite coloured in a turquoise colour has been used as a known and unknown turquoise replacement for nearly a century. Many people have been duped by magnesite dyed to resemble turquoise, while some have been duped into purchasing magnesite dyed to resemble lapis lazuli. When purchasing cabochons or tumbled stones with vibrant colours, be careful. Inquire whether they've been dyed. Scrubbing the substance with a cotton swab dipped in fingernail polish remover is a reasonably effective destructive test. Nail polish remover may be used to remove many of the dyes used on magnesite. Scratching the substance with a hardness pick or a nail may also reveal the bright white magnesite under the dyed surface.
Mineral Structure and Later Thermal Effects
The mineral properties of crystalline and cryptocrystalline magnesites are somewhat different. Cryptocrystalline magnesite is amorphous, consisting mainly of aggregates of fine grains, while crystalline magnesite has a well-developed crystal structure. Since clumped isotopic composition is determined by complex bonding, differences in the crystal structure are likely to influence how clumped isotopic signatures are recorded in these structures. As a result, later thermal events such as diagenesis/burial heating can alter their pristine signatures in different ways.
Properties of Magnesite
Magnesite in hand specimens can be difficult to classify since it often differs from its expected properties. Since it is frequently cryptocrystalline, its cleavage may be obscured. Magnesite is also silicified or mixed with chert, giving it a deceptively hard appearance. The apparent effervescence with HCl will be reduced if there is significant chert present.
The measures outlined below will most likely assist you in identifying magnesite. Some people believe you have a sample suitable for destructive testing.
To check for an acid reaction, scrape the specimen over a streak plate and make some powder. Then, on the specimen, drop a drop of dilute (5%) hydrochloric acid and watch for an effervescent reaction. To see tiny bubbles emerging slowly from the powder, you need a hand lens.
To determine the specific gravity, do the following: The real gravity of magnesite is normally between 3.00 and 3.20. If there is a lot of quartz or chert in it, it may be as low as 2.8. If the specimen contains substantial chert or is silicified, the low specific gravity will be accompanied by a higher than average hardness.
If your specimen has a polished surface and you have a refractometer (and know how to use it), you will be able to perform one of the most accurate magnesite tests. Magnesite has a birefringence of 0.191 and a refractive index ranging from 1.509 to 1.700. The fact that it experiences birefringence blink in the 1.509 to 1.700 range is the most valuable property.
Magnesite is a mineral that is composed of magnesium carbonate (MgCO3) and belongs to the calcite group of carbonate minerals. It is a major source of magnesium. The mineral formed as a result of the action of magnesium-containing solutions on calcite or as an alteration product from magnesium-rich rocks. Radenthein, Austria; the Liaotung Peninsula, Liaoning Province, China; and Clark County, Nevada, United States are notable deposits. Iron is normally present, and between magnesite and siderite, a complete chemical substitution sequence occurs in which iron replaces magnesium. Magnesite uses are: it can be used as a refractory material, as a catalyst and filler in the manufacture of synthetic rubber, and as a raw material in the manufacture of magnesium chemicals and fertilisers.