Brief information about some important minerals in terms of their nature and physical characteristics is given below:
- External crystal form: Determined by internal arrangement of the molecules- cubes octahedrons, hexagonal prism, etc.
- Fracture: Internal molecular arrangement so complex there are two planes of molecules; the crystal will break in an irregular manner, not along planes of cleavage.
- Lustre: Appearance of a material without regard to color; each mineral has a distinctive lustre like metallic, silky, glossy, etc.
- Streak: Colour of the ground powder of any mineral. It may be of the same colour as the mineral or may differ malachite is green and gives green streak.
- Structure: Particular arrangement of the individual crystal; fine, medium or coarse grained; fibrous separable, divergent and radiating.
- Specific gravity: The ratio between the weight of a given object and the weight of an equal volume of water; object weighted in air and then weighed in water and divide weight in air by the difference of the two weights.
