Minerals
- Are naturally occurring solids with a definite chemical composition and crystal structure.
- Minerals that are original components of rocks are called primary minerals (Feldspar, mica etc.).
- Minerals that are formed from changes in primary minerals and rocks are called secondary minerals (clay minerals).
- Those minerals that are chief constituents of rocks are called as essential minerals (Feldspars, pyroxenes, micas etc) and those which are present in small quantities, whose presence or absence will not alter the properties of rocks are called accessory minerals (tourmaline, magnetite etc).