minerals

Minerals are substances that are formed naturally in the Earth. Minerals are usually solid, inorganic, have a crystal structure, and form naturally by geological processes. The study of minerals is called mineralogy. A mineral can be made of single chemical element or more usually a compound.
      TYPES

              With over 3,000 different types of minerals a system is needed to make sense of them all. ... The Dana system divides minerals into eight basic classes. The classes are: native elements, silicates, oxides, sulfides, sulfates, halides, carbonates, phosphates, and mineraloids.     MINERALSMINERALS