Metamorphic Rocks Key info on the texture and structure of metamorphic rocks 3.0 / 5 based on 1 rating ? GeologyAS Created by: James BrockCreated on: 03-04-10 12:27 Metamorphic Rocks Size Regional Coarse - Gneiss Medium - Schist Fine - Slate All formed from regional metamorphism of mudstones and shales. Contact Marbles and metaquartzites become coarser the closer they are to the intrusion. Mudstones/shales hot = hornfels warm = spotted slate. Porphyroblastic Large crystals e.g. Garnet surounded by finer crystals e.g. micas in a Garnet Mica Schist 1 of 4 Shape 12 sided/Rhombic faced Garnets can be well formed 2 of 4 Orientation Random in contact metamorphisim Foliated in regional metamorphism High Grade foliation = Gneissose Banding Medium Grade Foliation = Schistosity Low Grade Foliation = Slatey Cleavage Preferred orientation 3 of 4 Texture Texture = SIZE SHAPE ORIENTATION 4 of 4
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