Igneous Rocks

Granite

     Igneous rocks are formed when melted rock deep in the Earth, called magma, cools and solidifies.  Magma may become trapped in underground pockets and cool slowly.  It may, instead, be forced to the surface of the planet and ejected from a volcano.  Ejected magma is called lava.  Either way, the result is called igneous rock.

Pumice

     Granite is an igneous rock which forms in slowly cooling pockets of magma that were trapped beneath the earth's surface.  After it cools, it is raised to the surface by tectonic forces.  Granite is composed of feldspar, hornblende, and quartz rock.

Obsidian

     Pumice is an igneous rock which forms when lava cools quickly above ground. You can see where air pockets were as it cooled. Pumice is very light and some actually float in water. 
     Obsidian is an igneous rock that forms when lava cools quickly above ground. It is glass-like and the edges are very sharp.

Basalt

     Basalt is another igneous rock that is formed when lava cools on the surface.  It is fine-grained and very heavy.