In order for a substance to be classed as a mineral it must be naturally occurring, solid and inorganic. Additionally, it must have a clearly defined structure and chemical composition. There are around 4,000 known minerals on Earth, and each of them has unique physical characteristics.
Substances that are classed as minerals must have the following properties:
- They must be naturally occurring
- Minerals are inorganic
- All are solid
- They must have a definite chemical composition
- An ordered internal structure
This means they are not man-made. For example, steel is not a mineral because it requires manufacturing.
Inorganic substances are those that are not produced by organisms. For example, wood is not a mineral because organisms produce it.
This means it cannot be a liquid or gas while subjected to normal temperature and pressure ranges.
This composition must fall within a defined range. For example, salt has a chemical composition of NaCl.
Mineral atoms have a set pattern and order. For example, halite features an equal number of salt and chlorine atoms following a cubic arrangement.
Each of the Earth's 4,000 minerals has a unique structure. This structure is defined by the color, cleavage, fracture, specific gravity, luster, hardness, magnetism, diaphaneity, streak, solubility and other defining factors. Scientists use these factors to determine how they can use minerals. For example, talc is an ideal foot powder when ground to a fine consistency.