Magnesite Magnesite

Magnesite - Definition and Overview

Magnesite
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General
CategoryMineral
Chemical formulamagnesium carbonate:MgCO3
Identification
Color White
Crystal habit usually massive, rarely as rhombohedrons or hexagonal prisms
Crystal system trigonal; bar 3 2/m
Cleavage[1011] Perfect, [1011] Perfect, [1011] Perfect
FractureBrittle - Conchoidal
Mohs Scale hardness 3.5 - 5
LusterVitreous
Refractive index Uniaxial (-) nω=1.508 - 1.510 nε=1.700
Pleochroism N/A
Streak white
Specific gravity 3.0 - 3.2
Fusibility infusible
Solubility Effervesces in hot HCl
Other Characteristics

Magnesite is magnesium carbonate, MgCO3. Iron (as Fe2+) substitutes for Mg with a complete solution series with siderite, FeCO3. Calcium, manganese, cobalt, and nickel may also occur in small amounts. Dolomite, (Mg,Ca)CO3, is almost indistinguishable from magnesite.

Magnesite occurrs as veins in and an alteration product of serpentine and other magnesium rich rock types in both contact and regional metamorphic terranes. These magnesites often are cryptocrystalline and contain silica as opal or chert.

References and external links

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