Plagioclase

minerals

albite

feldspar

anorthite

Images
Plagioclase feldspars form a continuous series of tectosilicates (framework silicates) from
anorthite to albite. They include
albite variety oligoclase (10% to 30% anorthite),
albite variety andesine (30% to 50% anorthite),
anorthite variety labradorite (50% to 70% anorthite) and
anorthite variety bytownite (70% to 90% anorthite),
as well as the end members.
Environments:

Plutonic igneous environments
Volcanic igneous environments
Metamorphic environments

The plagioclase feldspars are widely distributed as rock-forming minerals, and more abundant than the K-feldspars. They are minerals of the granulite facies. Plagioclase is an essential constituent of diorite, rhyolite, andesite and basalt.
It is a common constituent of quartzolite and also may be found in granite.
It is a mineral of the hornblende-hornfels, pyroxene-hornfels, amphibolite and granulite facies.

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