Magnesite is a mineral containing mixed crystals of iron II carbonate and magnesite. It has a layered structure formed by monolayers of carbonate groups alternating with magnesium monolayers as also iron II carbonate monolayers. Manganese, cobalt and nickel could also be present in small quantities.
Derivation of Name
It’s named so because of its chemical composition.
Magnesite crops up as veins in and as a modified product of ultramafic rocks, serpentinite and other rocks rich in magnesium in both regional and contact metamorphic lands. These magnesites are frequently cryptocrystalline and have silica in the form of chert or opal. Magnesite is also found within the Regolith above Ultramafic rocks as a secondary carbonate within soil and subsoil, where it gets deposited as a result of the disbanding of magnesium-containing minerals by carbon dioxide within ground waters.
Since Magnesite Cupels are capable of withstanding high temperatures, these are used in fire assay for the purpose of cupellation. Sometimes, dyed Magnesite is used for making beads for being used as ornaments.
An exciting Magnesite incident was reported in Brumado, Brazil, where a deposit of lucid, well formed, rhombohedrons similar to Iceland Spar Calcite was found. Prior to this finding, such crystals, though matching in appearance to Iceland Spar Calcite, were much rarer and adored. Common Iceland Spar Calcite has been incorrectly marked by some corrupt dealers as Magnesite to encourage sales.
Magnesite forms the calcite group of minerals, a group of related carbonates that are isomorphic to one another. They have many similar physical properties, and may partly or completely replace one another, forming a series of solid solution. All members of the calcite group crystallize in the trigonal system, possess a faultless rhombohedral cleavage and demonstrate sturdy double refraction in clear rhombohedrons.
Colorless, pale yellow, white, faintly pink, pale brown and lilac-rose.
Mohs scale hardness
3.5 - 4.5