Minerals
A mineral can be compared to a word of our language. We combine letters to form a word, and nature combines certain chemical [elements] to form each particular mineral. For example, [calcite], a mineral that is abundant in Texas, is always made up of the same proportions of the same three elements: calcium, carbon, and oxygen.
A mineral is made up of chemical [elements]. The mineral [calcite], for example, always consists of the same proportions of calcium, carbon, and oxygen.
Each mineral has its own characteristic internal structure and other properties. At ordinary temperatures, nearly all the minerals are solids rather than gases or liquids. (Water and mercury are the principal exceptions.) In addition, minerals are inorganic rather than being composed of plant or animal matter.
When a single chemical [element] is found alone in nature as a solid, it is considered to be a mineral, too. [Gold], silver, copper, lead, and [sulfur] are some of the chemical elements that can occur alone as solid minerals. When they occur this way, we refer to them as native silver, native copper, or native sulfur. Although the element mercury is a liquid rather than a solid at ordinary temperatures, it too is a mineral when it occurs alone in nature. It is then called native mercury.