Perthite — Mineral Variety

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. There are many different types of Perthite. Perthite combinations are of Albite (and sometimes Oligoclase) intermixed with either Microcline or Orthoclase.

Types of Perthites:

Classified by Host:

Antiperthite - Perthite in which the potassium feldspar (i.e. Microcline and Orthoclase) forms first, and afterwards the sodium feldspar (i.e. Albite and Oligoclase) forms internally in the mineral.
Mesoperthite - Perthite in which the sodium feldspar (i.e. Albite and Oligoclase) forms first, and afterwards the potassium feldspar (i.e. Microcline and Orthoclase) forms internally in the mineral.

Classified by Size:

Cryptoperthite - Perthite in which the feldspar intergrowth is so fine it can only be detected with a microscope.
Microperthite - Perthite in which the feldspar intergrowth is very fine but it can be detected with an unaided eye.
Macroperthite - Perthite in which the feldspar intergrowth is large and is easily seen.

Classified by Type:

Perthite - Intergrowth of Albite (or Oligoclase) and Microcline.
Amazonite-perthite - Intergrowth of Albite (or Oligoclase) and green Microcline (Amazonite).
Orthoclase-perthite - Intergrowth of Albite (or Oligoclase) and Orthoclase.