Oligoclase
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Physical & Optical Properties
Category
Semi-Precious Gems
Mohs Hardness
6,0 – 6,5
Specific Gravity
2,62 – 2,67
Refractive Index
1,538 – 1,55
Crystal System
Triclinic
Luster
Vitreous,Pearly
Fracture
Conchoidal
Color
various
Birefringence
0,01
Mohs Hardness
Mohs Hardness: 6,0 – 6,5
1 Soft10 Hard
Crystal System
Value & Market
Price Tier
Moderate ($50-500/ct)
Where to Buy Oligoclase
Blue Nile
Fine jewelry retailer
James Allen
Gemstone jewelry
Brilliant Earth
Ethically sourced gems
Amazon
Wide selection
Links may earn a commission at no extra cost to you.
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.
6 to 6.5Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references
2.62 to 2.67Walter Schumann, Gemstones of the world (2001) More from other references
Perfect,GoodMichael O?Donoghue, Gems, Sixth Edition (2006) Perfect in one and good in another direction
ConchoidalMichael O?Donoghue, Gems, Sixth Edition (2006)
1.538 to 1.550Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references
Biaxial/-Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references
0.010Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references
WeakMichael O?Donoghue, Gems, Sixth Edition (2006)
Colourless to bluishWalter Schumann, Gemstones of the world (2001) More from other references
Blue (moonstone), Rayleight scattering of light by lamellar structure. Red (sunstone), red lepidocrocite or hematite platelets give the aventurescenceW. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparentUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Vitreous,PearlyWalter Schumann, Gemstones of the world (2001) On cleavage surfaces mother-of-pearl lustreMore from other references
Pale brownish white, pale brownMichael O?Donoghue, Gems, Sixth Edition (2006)
TriclinicWalter Schumann, Gemstones of the world (2001) More from other references
As a major part of many rocks, especially igneous rocks such as granites, syenites and pegmatites. Also in intermediate lavas, schists and some amphibolites.Michael O?Donoghue, Gems, Sixth Edition (2006)
Red hematite platelets (aventurism) - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 8
Oligoclase information at mindat.org
About Oligoclase
Oligoclase is a sodium calcium plagioclase feldspar forming a solid solution between albite and anorthite, occurring in colorless, white, yellowish, or gray masses and crystals with a vitreous luster in granites, metamorphic rocks, and syenites worldwide. It is notably the host mineral for sunstone (aventurine feldspar) when it contains oriented hematite or goethite platelet inclusions that produce a brilliant golden to coppery aventurescence. Gem-quality sunstone oligoclase comes principally from Oregon (USA), Norway, and India.
Jewelry Use
Durability
5/10
Science FYI Family
Frequently Asked Questions
What is Oligoclase?
Oligoclase is a sodium calcium plagioclase feldspar forming a solid solution between albite and anorthite, occurring in colorless, white, yellowish, or gray masses and crystals with a vitreous luster in granites, metamorphic rocks, and syenites worldwide. It is notably the host mineral for sunstone
What is the hardness of Oligoclase?
Oligoclase has a Mohs hardness of 6.0 to 6.5, making it moderate for use in jewelry.
What color is Oligoclase?
Oligoclase is primarily Various.
How much does Oligoclase cost?
Oligoclase falls into the Moderate ($50-500/ct) price range. Prices vary based on color, clarity, cut, and origin.
What is the crystal system of Oligoclase?
Oligoclase belongs to the Triclinic crystal system.