April 6 Igneous Rocks
A rock may be made of one or more minerals.
I.
Igneous Rocks – root ignis meaning fire.
A. Extrusive rock – lava that erupted onto Earth’s surface. Ex. Basalt. (ex –
out)
1. Texture of extrusive rock is fine-grained or no crystal structure due to
quick hardening. Crystals are so small you need a microscope to see
them or may be missing.
B. Intrusive rock – hardened beneath the Earth’s surface. ( in – without) Ex.
Granite
1. Cools slowly so large rock crystals can form. Coarse-grained has large
crystals.
C. Uses for Igneous rock
1. Building materials – granite used by Egyptians and Incas
2. Statue material
3. Bridges and roadways
4. Kitchen counters -granite
5. Gravel – basalt
6. Pumice & obsidian for cleaning and polishing