Specific gravity is synonymous with density. It is defined as the relationship between the weight of an equal volume of water and the weight of the substance. To determine by calculation, it is equal to the weight of the mineral from the air divided by its loss of weight in water. Several methods are used to determine the specific gravity of solids. These are the used of the chemical balance, sometimes called hydrostatic method; the use of the Pycnometer, the use of the heavy liquids and the Nestphal balance, the Jolly balance and the Kratsehmar direct-reading balance.

Fracture

The fracture of the solid describes the character of the surface obtained when it is broken contrary to its natural cleavage planes. Amorphous substances are commonly prone to show fractured surfaces after breaking since they have no cleavage or parting. They usually appear as irregular and non-parallel cracks visible by slight adjustments of the condenser lens of polarized light microscopes.

There are several types fractures shown by different substances:

Conchoidal fracture – fractured surfaces appear to be curved and shell-like.
Even fractures – fractured surfaces appear to be smooth and even.
Uneven fractures – fractured surfaces appear to be rougher.
Splintery fractures – fractured surfaces of more or less fibrous minerals.