What are the properties of plagioclase?

What is plagioclase feldspar mineral used for?

Plagioclase is used in the manufacture of glass and ceramics; the iridescent varieties peristerite and labradorite are valued as gemstones or ornamental material. The primary importance of plagioclase, however, derives from its role in rock formation.

What are the two end members of the plagioclase series?

The Plagioclase series is a group of related feldspar minerals that essentially have the same formula but vary in their percentage of sodium and calcium. Albite and Anorthite are the end members of the series, with the intermediary minerals Oligoclase, Andesine, Labradorite, and Bytownite.

Is feldspar a mineral?

Feldspar is by far the most abundant group of minerals in the earth’s crust, forming about 60% of terrestrial rocks. Chemically, the feldspars are silicates of aluminium, containing sodium, potassium, iron, calcium, or barium or combinations of these elements.

What is the difference between orthoclase and plagioclase feldspar?

Plagioclase feldspars lack potassium, are light colored and are usually striated. Orthoclase is the more common of the k-spars. The differences between these minerals are minor in hand samples. Microcline tends to be deeper-colored and is the only one that can be, but is not always, a blue-green color (amazonite).

How are the intermediate members of plagioclase similar?

The intermediate members of the plagioclase group are very similar to each other and normally cannot be distinguished except by their optical properties. The specific gravity in each member (albite 2.62) increases 0.02 per 10% increase in anorthite (2.75).

What is the chemical composition of plagioclase minerals?

Plagioclase. Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series…

Which is the best description of plagioclase feldspar?

Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series (from the Ancient Greek for oblique fracture, in reference to its two cleavage angles).

How is plagioclase used as a diagnostic tool?

Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or ‘record-groove’ effect. Plagioclase is a major constituent mineral in the Earth’s crust, and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks.