Chapter 4: Rocks
Lava is extrusive magma, melted minerals mixed together. What does "extrusive" mean?
Five different granite samples, cut and polished. They formed from different magmas, and so the mineral mixtures are different, and even the minerals can have slightly different chemical compositions. Therefore, feldspar, quartz, mica, and hornblende occur in different amounts and with slightly different compositions in each sample of granite. Can you see the crystals? Is granite intrusive or extrusive? Do you think that these granites formed by cooling rapidly or gradually? What's the clue?
What is this diagram all about? You should be able to discuss what each arrow means. Could there be other arrows?