Name:____________
Class Period:__________
Igneous Rock Composition (40 Points)
Introduction: Below you will find a rock identification chart, used to identify igneous rocks. There are 9
common igneous rocks in the chart;
 Basalt
 Rhyolite
 Diorite
 Andesite
 Peridotite
 Grandiorite and
 Dacite
 Gabbro
 Granite.
The First row of the chart contains the names of Volcanic Rocks also known as extrusive rocks, while the
second row contains the names of plutonic or instrusive rocks. The third row contains a complex
diagram which shows the different minerals that make up each rock. Using this chart you can either
identify the sample name based upon the different amounts of minerals in the sample, or you can
describe the mineral content of the rock.
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2.
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6.
7.
1. Plutonic rocks are also know by what term?
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2. Where do these type of rocks form?
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3. List the plutonic rocks from the chart above
I.
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II.
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III.
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IV.
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V.
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4. Volcanic rocks are also know by what term?
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5. Where do these type of rocks form?
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6. List the volcanic rocks from the chart above
I.
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II.
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III.
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IV.
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7. Is basalt an intrusive or extrusive rock?
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8. What type of texture does Gabbro have?
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9. What is the composition of both Gabbro and Basalt?
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10. Name a coarse-grained igneous rock with the least pyroxene.
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11. Which intrusive rock contains the most plagioclase by volume?
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12. Which rock contains more quartz, Dacite or Granite?
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13. What rocks contain pyroxene, plagioclase and orthoclase?
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14. What is the most abundant mineral in Grandiorite?
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15. List the minerals present in Andesite.
I.
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II.
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III.
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IV.
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V.
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16. Identify the intrusive rock with the following characteristics; 40% plagioclase, 20% pyroxene, 10%
biotite, and 10% hornblende.
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17. Estimate the percentage of each mineral in Gabbro
 Olovine
 Pyroxene
 Plagioclase feldspar
 Biotite mica
 Amphiboles (hornblende)
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18. List the percentages of the following minerals in Granite
 Potassium Feldspar
 Quartz
 Plagioclase Feldspart
 Biotite Mica
 Amphibole (hornblende)
 Pyroxene
 Olivine
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