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