What elements make up plagioclase feldspar?

The feldspars are divided into 2 broad categories: plagioclase, which contains calcium and sodium; and orthoclase, which contains potassium.

What is the composition of plagioclase?

Plagioclase Mineral Data

What are the common elements in feldspar?

All the rock-forming feldspars are aluminosilicate minerals with the general formula AT₄O₈ in which A = potassium, sodium, or calcium (Ca); and T = silicon (Si) and aluminum (Al), with a Si:Al ratio ranging from 3:1 to 1:1.

How is plagioclase feldspar formed?

Plagioclase is a common clast produced during the weathering of igneous and metamorphic rocks. It can be the most abundant clast in sediments located close to their source area and decreases in abundance downstream.

What is feldspar composed of?

The mineralogical composition of most feldspars can be expressed in terms of the ternary system Orthoclase (KAlSi3O8), Albite (NaAlSi3O8) and Anorthite (CaAl2Si2O8). Chemically, the feldspars are silicates of aluminium, containing sodium, potassium, iron, calcium, or barium or combinations of these elements.

What type of mineral is plagioclase feldspar?

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.

What minerals is plagioclase made of?

Plagioclase is a member of the feldspar group (like orthoclase) and is a framework silicate. Plagioclase consists of a solid solution between the albite and anorthite end-members, and together with quartz is the most common of the rock forming minerals.

How is plagioclase feldspar different from orthoclase feldspar?

The key difference between orthoclase and plagioclase is that orthoclase appears in green-yellow colour, whereas plagioclase appears in white colour. Orthoclase and plagioclase are important minerals. Both these forms are members of the feldspar group.

What color is plagioclase feldspar?

Plagioclase feldspar is identified by its non-metallic, vitreous to pearly luster; white to dark gray color; and two good cleavages at nearly 90o. Plagioclase feldspar has striations on some cleavage surfaces.

Is plagioclase feldspar felsic?

Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars (albite-rich).

What type of twinning does plagioclase have?

Albite Twin Law

Plagioclase commonly shows this type of twinning, called the Albite Twin Law, with {010} as the twin plane. Such twinning is one of the most diagnostic features of plagioclase.

What are plagioclase and pyroxene minerals?

In Earth’s crust, pyroxenes are found in a wide range of igneous and metamorphic rocks. They are most abundant in the dark-colored igneous rocks, such as basalt and gabbro, that comprise most of the oceanic crust. Pyroxenes and plagioclase feldspar are the most abundand minerals in these rocks.