Igneous:
Igneous rocks form when hot lava cools and becomes solid all igneous rocks do not cool the same way. Also, that is why they do not look all the same. Some cool slowly and deep under the earth's surface. These are called intrusive igneous rocks. The slow cooling formed rocks with large crystals like Granite is an example of a rock that cooled slowly and has large crystals. Other rocks formed when the magma erupted from a volcano and reached the earth's surface through long cracks. However, magma is called lava when it reaches the earth's surface. They are called extrusive igneous rocks some examples of this type of rock is obsidian is an example of another extrusive igneous rock that cooled so fast that it has no crystals and looks like shiny, black glass.