For this activity you will need to watch the short video(s) for each igneous rock. You have been provided with key characteristics for each igneous rock on the page with the igneous rock videos. You will need to identify each igneous rock by comparing that information with the table below to determine the rock name. Once you have determined the rock name you will need to create an excel table with the following columns and in this order:
Sample Number, Texture, MCI, Minerals, Name, and How Formed. You will be submitting this completed excel table. You need to put the samples in numeric order in the chart.
You will use the chart below to determine the rock name and then you can obtain the remaining information and MCI needed to complete making your table.
You will use the the knowledge you have gained from the readings and videos to determine how the rock formed i.e. is it plutonic/intrusive (cooled slowly below the earth) or volcanic/extrusive (cooled quickly on the earth’s surface).
Each sample is worth 3 points.
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Mafic Color Index (MCI) |
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Felsic |
Intermediate |
Mafic |
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Mineralogy |
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10-20% quartz, more alkali feldspar than plagioclase and less than 15% Fe-Mg rich minerals |
No quartz, more plagioclase than alkali feldspar, and more than 20% Fe-Mg rich minerals |
No quartz or alkali feldspar, some plagioclase and more than 40% Fe-Mg rich minerals |
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TEXTURE |
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Pegmatitic |
Granite Pegmatite |
Diorite Pegmatite |
Gabbro Pegmatite |
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Phaneritic |
Granite |
Diorite |
Gabbro |
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Aphanitic |
Rhyolite |
Andesite |
Basalt |
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Porphyritic |
porphyritic rhyolite |
porphyritic andesite |
porphyritic basalt |
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Glassy |
Obsidian applies to all three MCI’s |
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Vesicular |
Pumice |
Scoria |
vesicular basalt |
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Pyroclastic |
Welded tuff or Volcanic tuff |
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Modified from: http://facweb.bhc.edu/academics/science/harwoodr/g… and https://www.wou.edu/las/physci/taylor/gs104/ES104_…
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