Feldspar

Big Photo

Moonstone
Myanmar
4.57 carats
© Palagems

Feldspar is derived from German "Feld"- field and "Spath" - a rock that does not contain ore.

There are two main subgroups that produce gems: the potassium feldspars and the plagioclases (a series from calcium to sodium feldspars).

Feldspar Gemstones by Colour

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

Feldspar Gemstones by Size

This table shows distribution of Feldspar 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:0.07 cts
Heaviest:145.2 cts
Average:9.07 cts
Total photos:305
Do you have a larger Feldspar? Why not upload a photo?
0.07ct to 14.58ct14.58ct to 29.10ct29.10ct to 43.61ct43.61ct to 58.12ct58.12ct to 72.64ct72.64ct to 87.15ct87.15ct to 101.66ct101.66ct to 116.17ct116.17ct to 130.69ct130.69ct to 145.20ct
General Information
Varieties/Types:
Albite - Sodium-rich Feldspar.
Andesine - A plagioclase feldspar with an Albite: Anorthite molar ratio ranging from 50:50 to 70:30.
Anorthite - Calcium-rich Feldspar.
Bytownite - A plagioclase Feldspar with an Albite: Anorthite molar ratio ranging from 10:90 to 30:70.
Labradorite - A plagioclase Feldspar with an Albite: Anorthite molar ratio ranging from 30:70 to 50:50.
Spectrolite - Trade name for a Labradorite from Finland that shows the spectral colours especially effectively.
Microcline - A triclinic Potassium Feldspar.
Amazonite - A green to blue-green variety of Microcline.
Oligoclase - A plagioclase feldspar with an Albite: Anorthite molar ratio ranging from 90:10 to 70:30.
Orthoclase - A monoclinic Potassium Feldspar.
Adularia - A gemmy colourless variety of Orthoclase.
Moonstone - A variety of Orthoclase that exhibits a strong blue adularescence.
Sanidine - A triclinic Potassium Feldspar found in lavas.
Sunstone - A Plagioclase Feldspar, which exhibits aventurescence when viewed from certain directions.
Photos of natural/un-cut material from mindat.org
Physical Properties of Feldspar
Mohs Hardness6 to 6.5
Walter Schumann, Gemstones of the world (2001)
Specific Gravity2.56 to 2.75
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityPerfect
Walter Schumann, Gemstones of the world (2001)
FractureUneven,Conchoidal,Splintery
Walter Schumann, Gemstones of the world (2001)
Optical Properties of Feldspar
Refractive Index1.518 to 1.570
Walter Schumann, Gemstones of the world (2001)
Birefringence0.008 to 0.010
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)Colourless, yellow, green, blue-green, orange, red-brown, dark gray, gray-black.
Walter Schumann, Gemstones of the world (2001)
TransparencyTransparent,Translucent,Opaque
Walter Schumann, Gemstones of the world (2001)
Further Information
Mineral information:Feldspar information at mindat.org
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