Bytownite

Big Photo

Mexico
5.63 carats
© Rarestone.com

A rare form of Feldspar, comprises 10-30% Albite and 70-90% Anorthite feldspar. Some of the stones have a distinct resemblance to Andalusite.

Bytownite Gemstones by Colour

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

Bytownite Gemstones by Size

This table shows distribution of Bytownite 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:0.21 cts
Heaviest:7.08 cts
Average:2.52 cts
Total photos:19
Do you have a larger Bytownite? Why not upload a photo?
0.21ct to 0.90ct0.90ct to 1.58ct1.58ct to 2.27ct2.27ct to 2.96ct2.96ct to 3.65ct3.65ct to 4.33ct4.33ct to 5.02ct5.02ct to 5.71ct5.71ct to 6.39ct6.39ct to 7.08ct
General Information
A variety or type of:Feldspar
Chemical Formula
Ca(70-90%)Na(30-10%)(Al,Si)AlSi
 
2
O
 
8
Michael O’Donoghue, Gems, Sixth Edition (2006)
Photos of natural/un-cut material from mindat.org
Physical Properties of Bytownite
Mohs Hardness6 to 6.5
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Specific Gravity2.72 to 2.75
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
TenacityBrittle
Michael O’Donoghue, Gems, Sixth Edition (2006)
Cleavage QualityPerfect
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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FractureUneven,Conchoidal
Michael O’Donoghue, Gems, Sixth Edition (2006)
Optical Properties of Bytownite
Refractive Index1.561 to 1.583
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Optical CharacterBiaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.007 to 0.011
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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DispersionLow (0.012)
Michael O’Donoghue, Gems, Sixth Edition (2006)
Colour
Colour (General)Yellowish, reddish-brown, labradorescent
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
TransparencyTransparent,Translucent
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
LustreVitreous,Dull (Earthy)
Michael O’Donoghue, Gems, Sixth Edition (2006) Vitreous to dull
Crystallography of Bytownite
Crystal SystemTriclinic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Geological Environment
Where found:It is usually found as compact masses and grains in gabbros, norites, allivalites and anorthosites. It also forms from sodic metasomatism of metamorphic rocks. Often it occurs as part of compositionally zoned feldspars.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Bytownite information at mindat.org
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