Term
Igneous Rocks
2a - Pegmatitic Granite
Texture: Pegmatitic
Composition: Felsic
Very large crystals, in our samples there is a majority of pink, Potassium feldspar.
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Term
Igneous Rocks
1 - Diorite
Texture: Phanertic
Composition: Intermediate
About half light and half dark colored crystals. |
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Definition
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Term
Igneous Rocks
2b - Granite
Texture: Phaneritic
Composition: Felsic
Crystals are visible, but are quite small.
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Definition
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Term
Igneous Rocks
4 - Obsidian
Texture: Glassy
Composition: Felsic to Mafic, Dark Colored
Distinct glassy texture. |
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Definition
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Term
Igneous Rocks
3b - Pumice
Texture: Vesicular
Composition: Felsic to Intermediate
Very small vesicles, can be difficult to see.
Very light, floats on water. |
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Definition
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Term
Igneous Rocks
3a - Scoria
Texture: Vesicular
Composition: Mafic
Resembles a sponge, in our samples the holes (vesicles) are usually smaller in Scoria than in Vesicular Basalt (9a) |
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Definition
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Term
Igneous Rocks
6 - Peridotite
Texture: Phaneritic
Composition: Ultramafic
Green color due to large amounts of the mineral, Olivine.
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Definition
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Term
Igneous Rocks
5 - Rhyolite
Texture: Aphanitic
Composition: Felsic |
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Definition
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Term
Igneous Rocks
8 - Gabbro
Texture: Phaneritic
Composition: Mafic
Crystals visibl |
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Definition
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Term
Igneous Rocks
7 - Volcanic Tuff
Texture: Pyroclastic
Composition: Felsic to Mafic
May appear to be Vesicular, but upon closer inspection one can see fragments of preexisting rock in the holes. |
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Definition
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Term
Igneous Rocks
9b - Basalt
Texture: Aphanitic
Composition: Mafic
Can not see crystals, dark grey to black color. |
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Definition
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Term
Igneous Rocks
9a - Vesicular Basalt
Texture: Vesicular
Composition: Mafic
Our samples tend to have larger vesicles than scoria.
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Definition
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Term
Igneous Rocks
10 - (Porphyritic) Andesite
Texture: Porphyritic or Aphanitic
Composition: Intermediate
Light gray to brown color.
If an abundant number of larger crystals (phenocrysts) are present in the fine grained ground mass, then it is a porphyritic andesite.
If phenocrysts are few a far between, it has a aphanitic texture and is simply, Andesite. |
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Definition
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