How do you identify perthite?

How do you identify perthite?

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.

What is perthite and Antiperthite?

A perthite is an intimate intergrowth of sodic and potassic feldspar resulting from subsolidus exsolution (unmixing of two minerals). An antiperthite is an intergrowth arising due to exsolution where potassic feldspar is present as blebs or lamellae within a sodic feldspar.

Is perthite a mineral?

Perthite is an intergrowth of two different Feldspar minerals in one rock. Perthite is usually composed of veins or stripes of one feldspar running through a different feldspar.

How is perthite formed?

Perthite is the name given to an intergrowth of K-feldspar and albite-rich plagioclase that is produced by exsolution of the plagioclase from the potassium feldspar upon cooling of an original higher temperature, homogeneous solid solution of the two minerals.

What is another name for potassium feldspar?

Synonyms for potassium feldspar include: Potash Feldspar. Alkali Feldspar. K-spar.

How can you identify K-feldspar in a thin section?

In general, keys to identifying K-feldspar are its (lack of) color, its low birefringence, and its twinning. In thin section, microcline, orthoclase and sanidine are distinguished by their twinning, optical sign, and 2Vo.

What is Perthite geology?

perthite, any member of a class of alkali feldspars in which tiny crystals of sodium-rich feldspar (albite; NaAlSi3O8) are intimately intergrown with, but distinct from, tiny crystals of potassium-rich feldspar (orthoclase or, less commonly, microcline; KAlSi3O8).

Is Perthite a feldspar?

What kind of mineral is potassium feldspar?

Potassium feldspar refers to a number of minerals in the feldspar group, and containing potassium: Orthoclase (endmember formula KAlSi3O8), an important tectosilicate mineral that forms igneous rock. Microcline, chemically the same as orthoclase, but with a different crystalline structure.

How can you tell the difference between plagioclase and K feldspar?

The feldspars are divided into two main groups: Potassium feldspar (“K-spar”) and plagioclase (“plag”). Both display two cleavages and an overlapping range of colors, but only plagioclase displays tiny grooves on one cleavage known as striations.