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10 Cards in this Set
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Sedimentary rocks |
1. Layers (if rock has layering) Flat and soft or crumbly. Made of mud, sand, or gravel for Sedimentary and Igneous: layers are made of crystals, which are of different sizes in different layers. 2. Grains (if NO visible grains present) Looks like dry clay or mud Very Soft, easily scratched with fingernail. Reacts with drop of dilute HCl 3. Visible Grains present Contains Fossils (whole or fragmented leaves, stems, shells, footprints) Grains are mostly sand, silt, or gravel (clastic). Contains rounded grains (like pebbles) Contains grains that are fragments of other rocks (clastic). Grains are mostly mineral crystals Crystals can be easily scratched and/or broken apart. Crystals are Calcite (react with diffuse HCl) and crystals have different sizes and/or occur in layers. Crystals are mostly gypsum or halite. |
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Igneous |
1.Layers are made of crystals, which are of different sizes in different layers. (also for sedimentary) 2. NO visible grains present Looks glassy and dense and hard, like window glass. Very hard 3. Visible Grains present - grains are mostly mineral crystals Crystals are randomly oriented in very hard rock (also for metamorphic). Large crystals sit in a very hard mass with smaller crystals or no visible grains Crystals are mostly Olivine, feldspar, or pyroxene. 4.Additional features Rock is vesicular: has bubble-shaped holes/cavities or looks frothy. Rock is very hard and has ropy, streamlined flow structures. |
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Metamorphic |
1. Layers made of Crystals, which are about the same size in all layers. Layers are folded or otherwise deformed. 2. NO visible grains present Looks glassy--- and brittle, lightweight, opaque black, i.e. anthracite coal 3. Visible Grains present Contains fossils - and the fossils are so deformed (sheared, folded, or of changed composition) that they are barely recognizable. 3. Visible Grains present - grains are mostly mineral crystals Crystals are randomly oriented in very hard rock (also for igneous) Crystals are flat (eg mica) and foliated: lay parallel to one another, giving the rock a layered or scaly appearance. Long crystals are foliated: lay parallel to one another. Crystals are Calcite (react with diffuse HCl) -- and Equigranular: all about same size. Crystals are mostly garnet, micas (muscovite, biotite), serpentine, graphite, galena, or sphalerite. 4.Additional features Rock looks metallic (silvery, brasy, or copper-like) and scaly or smooth. |
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Rock Texture - Glassy |
no visible grains break along wavy, curved surfaces Igneous Rocks |
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Rock Texture - Fine-grained |
made mostly of grains that are barely visible and too small to identify (grains less then 1mm in diameter). |
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Rock Texture - Coarse-grained |
made mostly of grains that are visible and large enough to identify (more than 1mm diameter) |
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Rock Texture - Vesicular |
with round or oval holes (vesicles), like sponge. Holes are bubbles of volcanic gases that bubbled through the lava that cooled to make the rock before the bubbles could escape Example Vesicular Basalt: |
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Rock Texture - Crystalline |
Fine and Coarse Grained rocks in which the grains are intergrown mineral crystals that glitter when rotated in bright light. Crystals may be heterogranular (mix of two or more significantly different sizes) or equigranular (all about the same size). Foliated - randomly arranged, metamorphic texture in which minerals grains have been aligned or layered, causing the rock to break or reflect light in a specific direction like the layered scales on a fish. |
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Rock Texture - Clastic |
rock is mostly made of clasts (fragments of broken pieces) of minerals of other rocks. Bioclastic - rock made mostly of plant fragments or broken bones and shells). Clasts may be angular or rounded. (gravelly rocks, sandy rocks, clayey (made mostly of clay) ) |
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Rock Texture - Layered |
grains arranged in layeres that can be observed at more than one scale. Sedimentary rocks generally have flat layers, made of clastic grains (gravel, sand, silt, clay, shells, plant fragments) or crystals of gypsum, halite or calcite. Metamorphic rocks layers are generally not flat-lying and foliated, they also can be folded. |