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Elemental Composition (by mass)
| Element | Mass % | Visual |
|---|---|---|
| O Oxygen | 56.93% | |
| Mg Magnesium | 28.83% | |
| C Carbon | 14.25% |
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
IMA Abbreviation (Whitney-Evans 2010)
Mgs
→ Magnesite
Mg carbonate
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Pronunciation
/ˈmæɡnɪsaɪt/
↔ MAG-nuh-site
from magnesium
Mohs 4–4.5
Vickers (~) 200 HV
Knoop (~) 220 HK
Geological setting
HydrothermalSedimentaryEvaporite
Element composition by mass
Formula: MgCO₃ · molar mass: 84.31 g/mol
| O | 56.93% | |
| Mg | 28.83% | |
| C | 14.25% |
Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.
Mohs Hardness
4–4.5
Magnesite sits at 4–4.5 on the Mohs scale — can be scratched by a steel knife.
Colors:
Streak
White
White
Crystal system
Trigonal
Trigonal
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CarbonatesCarbonates
TL;DR · 1 min read
Magnesite (MgCO₃) is the magnesium end-member of the calcite-group carbonates. It forms by hydrothermal alteration of ultramafic rocks and as primary precipitate in evaporite basins.
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Magnesite (MgCO₃) is the magnesium end-member of the calcite-group carbonates. It forms by hydrothermal alteration of ultramafic rocks and as primary precipitate in evaporite basins. Brumado (Brazil) supplies gem-quality transparent magnesite; massive cryptocrystalline “porcelain magnesite” from Liaoning (China) is the dominant industrial source for refractories.