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Oligoclase

Big Photo

Kenya
1.59 carats
© Rarestone.com

A plagioclase series feldspar comprising 70-90% Albite.
The name oligoclase derived from the Greek "oligos" - little, and "clasein" - to break, because the mineral was thought to have a less perfect cleavage than albite. This name was given by August Breithaupt in 1826.

Oligoclase Gemstones by Colour

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

Oligoclase Gemstones by Size

This table shows distribution of Oligoclase 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:1.43 cts
Heaviest:3.82 cts
Average:2.26 cts
Total photos:9
Do you have a larger Oligoclase? Why not upload a photo?
1.43ct to 1.67ct1.67ct to 1.91ct1.91ct to 2.15ct2.15ct to 2.39ct2.39ct to 2.63ct2.63ct to 2.86ct2.86ct to 3.10ct3.10ct to 3.34ct3.34ct to 3.58ct3.58ct to 3.82ct
General Information
A variety or type of:Albite, which is a variety of Feldspar
Chemical Formula
Na(90-70%)Ca(10-30%)(Al,Si)AlSi
 
2
O
 
8
Michael O’Donoghue, Gems, Sixth Edition (2006)
Oligoclase Treatments
Irradiation may turn colourless material blue if lead and water impurities are present (see amazonite). Oligoclase has also been reported to turn orange and green upon irradiation.
Physical Properties of Oligoclase
Mohs Hardness6 to 6.5
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
Specific Gravity2.63 to 2.66
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
Cleavage QualityPerfect,Good
Michael O’Donoghue, Gems, Sixth Edition (2006) Perfect in one and good in another direction
FractureConchoidal
Michael O’Donoghue, Gems, Sixth Edition (2006)
Refractive Index1.538 to 1.550
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Optical CharacterBiaxial/-
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Birefringence0.010
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
More from other references
Dispersion
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