1. Properties of Igneous Rocks

2. Types of Igneous Rocks  Plutonic / Intrusive: These rocks formed from magma that crystallized and cooled slowly underground.  These rocks are coarse grained (have visible mineral crystals).

3. Volcanic – Extrusive Rocks  Extrusive rocks are formed when magma or lava cools quickly at or near the surface of the earth.  These rocks have a fine grained or glassy texture. Mineral crystals are either very small or microscopic.

4. Fine Grained

5. Glassy Texture

6. Glassy Texture with many air holes

7. Coarse grained

8. Porphyritic Texture  Sometimes magma cools at different depths and temperatures so some mineral crystals are large while others are small.

9. Magma Types  Felsic magma: Rocks made from this type of magma tend to be light colored, high in silica and have a large amount of quartz and or feldspar in them.

10. Mafic magma  This magma tends to form rocks that are dark colored, high in ferromagnesian minerals like hornblende, augite, olivine and biotite. (Dark minerals)