Earth Sciences 1022A/B Lecture 6: METAMORPHIC ROCKS
14 Feb 2019
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In response to this stress platy/elongate materials line up to produce a foliated texture: with increasing metamorphism shale turns into slate, phyllite, schist, gneiss, bedding, stratification, a sedimentary characteristic, produced by the deposition of sediment in horizontal layers. Phyllite: development of a more distinct silky sheen due to further growth of platy mica crystals relative to original clay particles (large crystals reflect light like tiny mirrors, foliation type : phyllitic foliation. Schist: appearance characterized by an obvious sparkle due to much larger mirror-like mica grains (able to be clearly seen with naked eye) In some cases, mica crystals are observed to wrap around larger round crystals of minerals such as garnet (these round crystals are called porphyroblasts: foliation type : schistose foliation. Non foliated metamorphic rock: some metamorphic rocks, whether formed by contact or regional metamorphism always have a non-foliated texture.
