Rocks vs. Minerals
Though some may look similar on the surface, rocks and minerals differ because minerals have definite chemical composition but rocks do not. Rocks are usually made up of two or more minerals. They may contain fossils, but minerals do not.
A rock is a large solid mass of consolidated or unconsolidated mineral matter. Geologists classify rocks as larger than pebbles, but smaller than boulders. Rocks are classified into three types, depending on how they are formed: sedimentary, metamorphic, and igneous. Some well-known rocks are gneiss, slate, and granite.
Minerals are inorganic homogeneous substances that form naturally under the ground. They are usually chemical compounds, but some, such as copper and gold, are elements. Some minerals are even required by the human body for nutrition. Some well-known minerals are quartz, salt, and petroleum.