Perthite Value, Price, and Jewelry Information

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Perthite Feldspar from Dan Patch pegmatite, Black Hills, South Dakota. By Jstuby at en.wikipedia (Transferred from en.wikipedia) [Public domain], from Wikimedia Commons

Perthite is a blend of microcline, albite and oligoclase. It is usually brown and white. May have gold or white iridescence.


Perthite Information

Data Value
Name Perthite
Is a Variety of Feldspar
Colors Brown, white.
Fracture Conchoidal, uneven, splintery
Hardness 6-6.5
Cleavage Perfect 2 directions
Crystallography Triclinic.
Birefringence Variable, depends on composition: 0.005-0.011
Luster Vitreous.
Specific Gravity 2.57-2.69
Transparency Transparent.
Phenomena Iridescence, schiller.


Perthite is an intergrowth of albite, oligoclase, plus orthoclase or microcline. The characteristic texture is produced by unmixing from high temperature. The appearance of the material depends on the cooling history, and hence the relative crystal sizes of the different feldspars in the mixture. Usually perthite consists of brown and white lamellae; the white feldspar often has a golden yellow or white Schiller. Perthitic intergrowths are very typical of the whole range of plagioclase compositions and therefore must be considered one of the most abundant mineral associations in nature.


Perthite is named for the locality, Perth, Ontario, Canada.


Fine perthite that is suitable for cutting comes from Dungannon Township, Ontario, Canada,in large pieces, and from various localities in Quebec, as well as from other countries.

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