Magnesite

Big Photo

Brazil
8.80 carats
© Rarestone.com

Magnesite is named from Greek "magnesia lithos" - magnesian stone, a kind of ore from Magnesia, the coastal district of ancient Thessaly, Greece.

Magnesite frequently occurs as translucent, sometimes transparent colourless, white, yellowish to brown or grey masses with an earthy or chalky appearance. This material is cut into cabochons.

Transparent crystals of gem-quality are very rare. The amount of faceted stones is mostly limited to specialized collections.

Magnesite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 

Magnesite Gemstones by Size

This table shows distribution of Magnesite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:3.51 cts
Heaviest:17.75 cts
Average:7.89 cts
Total photos:5
Do you have a larger Magnesite? Why not upload a photo?
3.51ct to 4.93ct4.93ct to 6.36ct6.36ct to 7.78ct7.78ct to 9.21ct9.21ct to 10.63ct10.63ct to 12.05ct12.05ct to 13.48ct13.48ct to 14.90ct14.90ct to 16.33ct16.33ct to 17.75ct
General Information
Varieties/Types:
Chemical Formula
MgCO
 
3
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Photos of natural/un-cut material from mindat.org
Magnesite Treatments
Dyed to imitate lapis, turquoise (chelsea: common reddish), coral. Acetone test - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 8
Physical Properties of Magnesite
Mohs Hardness3.5 to 4.5
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Specific Gravity2.92 to 3.12
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Cleavage QualityPerfect
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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FractureConchoidal
Arthur Thomas, Gemstones (2009)
Optical Properties of Magnesite
Refractive Index1.509 to 1.720
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterUniaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.190 to 0.202
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) DoublingMore from other references
PleochroismNil
Arthur Thomas, Gemstones (2009)
DispersionNil
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)White, yellow, brown, black, colourless
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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TransparencyTranslucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreVitreous,Dull
Walter Schumann, Gemstones of the world (2001)
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Fluorescence & other light emissions
Fluorescence (General)Blue, green, white common
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Fluorescence (Short Wave UV)Blue green or white fluorescence may be seen with greenish phosphorescence
Michael O’Donoghue, Gems, Sixth Edition (2006)
PhosphorescenceGreenish
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Magnesite
Crystal SystemTrigonal
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
HabitMassive
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Geological Environment
Where found:Magnesite occurs as a primary mineral in igneous or sedimentary rocks or may be formed by the metamorphism or alteration of serpentine and peridotite.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Magnesite information at mindat.org
Significant Gem Localities
Brazil
 
  • Bahia
    • Brumado (Bom Jesus dos Meiras)
      • Serra das Éguas
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 426
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 426
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