Identification of Igneous Rock
You have identified either porhorytic andesite or porphoytic diorite.
In order to ditinguish between the two take a closer look at the matrix. If the porphorytic texture can be descibed as large crystals in a phaneritic matrix then you have identified porphorytic Diorite. If, on the other hand, the porphorytic texture can be descibed as large crystals in an aphanitic matrix you have identified porphorytic andesite.
Texture |
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Felsic |
Intermediate |
Mafic |
Ultramafic |
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Pegmatitic |
Granite-pegmatite |
Diorite-pegmatite |
Gabbro-pegmatite |
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Phaneritic |
Granite |
Diorite |
Gabbro |
Rarely seen (Komatiite) |
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Aphanitic |
Rhyolite |
Andesite |
Basalt |
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Porphyritic |
Porphyritic Rhyolite |
Porphyritic Andesite |
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Glassy |
Obsidian |
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Vesicular |
Pumice |
Scoria |
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Pyroclastic |
Tuff |
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