Name _______________________________________ Chapter 2 Period _______ Code # ______ 18. What is meant by specific gravity or relative density ? 19. Define transparency . A substance allows light to pass through and can be seen through clearly . 20. Define translucent. A substance which allows some of the light to pass through and cannot be seen so clearly . 21. Define opaque . A substance that does not allow light to pass through at all . 22. What are rocks composed of? 23. How are rocks classified ? 24. How are igneous rocks formed ? 25. How are sedimentary rocks usually formed ? 26. How is a metamorphic rock created ? 27. Define texture. 28. What occurs when magma cools to about 600 to 1000 C? 29. What is meant by crystallization ? 30. What does the size of crystals indicate about igneous rocks ? 31. What size crystals results from slow cooling of magma? 32. What size crystal results from rapid cooling of magma? 33. What often occurs with super rapid cooling of magma?