Magnesite (Var. mesitite) Locality : Freiberg District, Erzgebirge, Saxony, Germany Size : 9.5x6.4cm — Photo: Didier Descouens · CC BY-SA 4.0
Magnesite
Magnesium carbonate — a white mineral of altered ultramafic rocks and magnesian limestones, source of magnesia refractories.
Intro adapted from Wikipedia (CC BY-SA).
Magnesite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Mg(CO₃).
It crystallizes in the hexagonal crystal system (space group R-3c). It is a member of the Calcite structural group.
Key properties: Mohs hardness 3.5–4.5; specific gravity 3; typically white or colorless or gray or yellow or brown; White streak; Vitreous luster; refractive index 1.573; optically uniaxial.
IMA symbol Mgs, IMA status: approved, named in 1808.
Found as a primary mineral in igneous or sedimentary rocks; formed by metamorphism or alteration of serpentine and peridotite; uncommon in marine evaporites and hydrothermal veins; rare in carbonatites.
It is found associated with Talc, antigorite, “chlorite”, dolomite, calcite.
The name refers to magnesium in the composition.
Collections: Everyday Minerals, Collector Favorites.