Identifying Rocks and Minerals/Differences Between Rocks and Minerals

What's the difference between rocks and minerals?
A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure formed by geological processes. A rock is an aggregate of one or more minerals whereas a rock may also include organic remains and mineraloids. Some rocks are predominantly composed of just one mineral. For example, limestone is a sedimentary rock composed almost entirely of the mineral calcite. Other rocks contain many minerals, and the specific minerals in a rock can vary widely. Some minerals, like quartz, mica or feldspar are common, while others have been found in only one or two locations worldwide. An easier explanation would be that a rock can contain minerals whereas a mineral has a unique specific makeup and always has the same composition if it's the same mineral. Rocks are always minerals, but not all minerals are rocks. Like all chemicals, minerals have a chemical formula; for example amethyst's formula is SiO2.