These minerals have two perpendicular planes of cleavage and thus tend to form irregular rectangular blocks, and one of the t
These minerals have two perpendicular planes of cleavage and thus tend to form irregular rectangular blocks, and one of the two major classes of these minerals display striations along cleavage planes. Examples of these minerals include labradorite and microcline, and the evolution of these minerals is described by the continuous branch of Bowen's Reaction Series. These minerals are grouped as being alkalai or plagioclase, and the orthoclase type of these aluminosilicate minerals defines a Mohs hardness value of six. Granite is primarily composed of quartz and these minerals. For 10 points, name this most abundant type of mineral on Earth.
These minerals have two perpendicular planes of cleavage and thus tend to form irregular rectangular blocks, and one of the two major classes of these minerals display striations along cleavage planes.
feldspars [accept alkali feldspars or K-feldspars or potassium feldspars before "labradorite"]