GEO 2163 Lecture Notes - Lecture 10: Plagioclase, Dodecahedron, Gabbro
21 Sep 2017
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Document Summary
Crystals commonly tabular, divergent aggregates, granular, cleavable massive. Crystals typically thin and tabular, rhombic in cross section, striated; massive. Grains are commonly elongate with a tabular appearance . blocky, tabular crystals. Perfect on {001}, very good on {010}, imperfect on {110} Perfect on {001}, less perfect on {010}, intersecting at near. Greyish yellow, white, pink white in many silicic intrusive igneous rocks such as granites, granodiorite, syenite in particular in shallow intrusions. Microcline, the lowest temperature k feldspar, is more abundant in deep plutonic rocks. Grains are commonly elongate with a tabular appearance. May contain lamellae which formed from exsolved albite blocky crystals. It can be difficult to see cleavage in thin section due to microcline"s low relief. White, cream, light yellow, light brown, reddish-brown, pink, light blue, blue-green, green, deep green. Sometimes multicolored with alternating green and white color. white. When euhedral usually stubby prisms with hexagonal or square prisms trapezohedral crystals with an eight-sided or rounded section.
