We are comparing rocks and minerals. Minerals are naturally occurring, atmospherically stable, and composed of definite chemical compositions with specific ordered molecular configurations. They also have specific physical properties. Some measures of these properties include color, luster, fracture, cleavage, hardness, and streak. Rocks are composed of more than one mineral and also non-mineral matter. Rocks have no distinctive chemical composition or physical properties. There are three major categories of rock: igneous, metamorphic, and sedimentary. One example of the relationship between rocks and minerals is granite. Granite is a rock that is composed primarily of three different minerals: quartz, feldspar, and biotite.