Igneous

Gabbro was created with faster cooling than Granite. Because it cooled quicker, darker minerals such as Biotite, Pyroxene (darker minerals) and Plagioclase Feldspar (white minerals). The bottom picture is a cross section of Gabbro showing the mineral grains.

Because Diorite didn't cool quickly or slowly, it has more of the white minerals (Quartz and Plagioclase feldspar) than Gabbro. It contains Hornblende and Biotite as the black minerals. Pink (Potassium Feldspar) is absent though since it requires slow cooling.

Granite is the slowest cooled Igneous rock. The pink is Potassium Feldspar. It is formed by slow cooling of magma deep within the earths surface. The cross section shows clearly the individual minerals the rock is made from - Feldspar, Quartz and Hornblende/Biotite. Granite is used for counter tops.

Basalt is created by lava. It is relatively fast cooling. First Nations peoples traditionally used this fine grained rock for heating up water as well as for tomahawks.

Obsidian is also known as volcanic glass. Because it is very sharp when broken, it has been traditionally used and traded by First Nations peoples for knives and arrow heads. They are the black rocks in the pics above.

When lava is mixed with air and cools fast to trap the bubbles, it creates pumice. Darker pumice generally sinks in water, but lighter coloured pumice traps enough air that it floats in water! People use it today to scrub in the bath.