Lab 6

Geology 111G Module 6 Lab Metamorphic Rocks ID Metamorphic Rock Identification Sample number Metamorphic Texture Parent rock Rock name 1 Foliated Schist Gneiss 2 Foliated Slate Schist 3 Non-Foliated Limestone Marble 4 Foliated Mudstone Slate 6 Non-Foliated Sandstone Quartzite 8 Non-Foliated Bituminous Coal Anthracite Coal Comparing Metamorphic Rocks 1. Comparing Rocks #1 and #2 which one do you think formed under more pronounced (higher temperatures and/or higher pressures) metamorphic conditions? Explain. Gneiss generally forms under more pronounced (higher temperatures and/or higher pressures) metamorphic conditions compared to schist. The key difference lies in the degree of metamorphic intensity and the resulting textures. Gneissic texture is characterized by the segregation of minerals into light and dark bands or layers. The segregation of minerals into light and dark bands or layers defines gneissic texture. These bands have a unique look because they frequently consist of alternating layers of various minerals. Gneiss often develops under extreme metamorphic circumstances. This indicates that it experiences intense heat and pressure. Schist is characterized by the preferred orientation of platy minerals like micas. Schist has a foliated look due to the minerals' frequent parallel alignment. Compared to gneiss, schist forms at lower to intermediate metamorphic conditions. While still considerable, the temperature and pressure are not as high as those that gneiss would encounter. 2. Using the rocks #3 & #4 answer the following: a. Which one formed under contact metamorphic conditions? Explain. Marble: Forms under Contact Metamorphic Conditions Limestone undergoes metamorphism to produce marble, a metamorphic rock. It often happens in contact metamorphism environments when molten magma intrusion subjects pre-existing rocks like limestone to high temperatures and pressures. The heat from the magma allows the original minerals to re-crystallize, turning the limestone into marble.