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Across 1. classified principally according to the minerals they consist of and on their chemical composition 7. The vast majority of the Earth's surface 8. a rock consisting of individual stones that have become cemented together 9. a naturally occurring glass formed as an extrusive igneous rock 13. esults from partial melting of a mafic rock above a subduction zone 14. currently known only on Earth where it forms a major part of continental crust. 16. fine-grained, foliated, homogeneous, metamorphic rock 17. It is usually gray to black and fine-grained due to rapid cooling of lava 18. textural term for a volcanic rock 19. nonfoliated metamorphic rock resulting from the metamorphism of limestone

Down 2. Fine-grained aquifer 3. can be considered as the extrusive equivalent to the plutonic granite rock 4. the largest source of fuel for the generation of electricity world-wide 5. name of a sedimentary carbonate rock 6. very resistant to chemical weathering and often forms ridges and resistant hilltops 10. rock composed of angular fragments of several minerals 11. fine-grained metamorphic rock 12. metamorphic rock with a high hardness 15. commonly known as rock salt.