1. Which is usually a characteristic of igneous rocks 6. Olivine and pyroxene are commonly found in igneous with a high density? rocks that are A) They are light in color. A) felsic, with low density B) They are felsic. B) felsic, with high density C) They have a high aluminum content. C) mafic, with low density D) They contain iron. D) mafic, with high density 2. Most igneous rocks form by which processes? 7. Which property is common to most dark-colored igneous rocks? A) melting and solidification B) heat and pressure A) high density C) erosion and deposition B) intrusive formation D) compaction and cementation C) abundant felsic minerals 3. Which property would be most useful for identifying D) coarse-grained texture igneous rocks? 8. Rock X and rock Y are igneous rocks with identical mineral composition. Rock X has no visible crystals A) kind of cement and rock Y has large, visible crystals. What can be B) mineral composition inferred about rock Y? C) number of minerals present D) types of fossils present A) It cooled at the Earth's surface, more slowly than rock X. 4. Which minerals are found in the igneous rocks gabbro B) It cooled beneath the Earth's surface, more and basalt? slowly than rock X. A) olivine and quartz C) It cooled at the Earth's surface, more quickly B) olivine and pyroxene than rock X. C) pyroxene and orthoclase D) It cooled beneath the Earth's surface, more D) orthoclase and quartz quickly than rock X. 5. Which diagram below shows an area in which fine-grained igneous rocks are most likely to be found? A) B) C) D) Base your answers to questions 9 through 13 on the table below which provides information about the crystal sizes and the mineral compositions of four igneous rocks, A, B, C, and D. 9. Which two rocks most likely formed farthest below the surface of Earth? A) A and B B) B and C C) C and D D) A and D 10. The mineral quartz in rock A is composed of the two most abundant elements by mass in Earth's crust. These two elements are oxygen and A) magnesium B) silicon C) iron D) lead 11. Which characteristic of rock B could be caused by the minerals pyroxene and olivine? A) green color B) felsic composition C) folded layers D) metallic luster 12. Rock B most likely is A) conglomerate B) schist C) obsidian D) peridotite 13. Which diagram best represents the texture, composition, and intergrown crystals of rock A? A) B) C) D) 14. Which process is necessary for the formation of igneous rocks? A) erosion B) deposition C) solidification D) metamorphism 15. The graph below shows the relationship between the cooling time of magma and the size of the crystals produced. Which graph correctly shows the relative positions of the igneous rocks granite, rhyolite, and pumice? A) B) C) D) Answer Key igneous rocks 1. D 2. A 3. B 4. B 5. C 6. D 7. A 8. B 9. A 10. B 11. A 12. D 13. C 14. C 15. A.