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Across 3. The process of digging up different materials from the ground. 4. glass is mainly made up of .... 8. A natural volcanic glass found as a kind of igneous rock. 9. What is the catalyst used in the manufacture of ammonia? 12. C........ is the breakdown of materials due to chemical reactions. 13. A metal used in cars which is more expensive than iron. 15. glass is used for windows because it is ........... 16. An example of a composite material is r........d c......e

Down 1. Ammonia is vitally important for w...d f..d pr......on 2. What is molten rock that erupts onto the surface called? 5. granite has large crystals which are cause by slow ... 6. iron corrosion is called ....... 7. iron is ma.....c 9. Rocks formed from molten magma 10. what will increase the yield of ammonia? 11. the first level of the earth's structure 14. A metamorphic rock made from limestone.