For 10 points, name this class of silicate minerals, which makes up about 60% of the earth's crust and has a Mohs hardness of six.
Arkoses are sandstones with substantial amounts of this type of mineral. One type of this mineral can be identified by its two cleavage angles and a banding pattern known as polysynthetic twinning. One type of this mineral is an intermixture formed when its original phase exsolves; that potassium-heavy type of this mineral is called perthite. Albite and (*) anorthite are end-members of a series of one type of this class of mineral. These weather into clay minerals. The continuous branch of Bowen's reaction series runs from the calcium rich to sodium rich types of one member of this class of minerals, plagioclase, before reaching another member, orthoclase. For 10 points, name this class of silicate minerals, which makes up about 60% of the earth's crust and has a Mohs hardness of six.
Arkoses are sandstones with substantial amounts of this type of mineral.
feldspar