Specific Gravity

What is specific gravity?
Specific gravity is the "heaviness" of a mineral. It is defined as a number that expresses the ratio between the weight of a mineral and the weight of an equal volume of water. Water has a specific gravity of “1.”

What is specific gravity dependent upon?
The specific gravity depends on:

  • The kind of atoms that comprise the mineral.
  • How the atoms are packed together.

You can easily distinguish minerals that have unusually high or unusually low specific gravities just by the way they "feel" when you hold a sample in your hand.

How is specific gravity measured?
The steps in measuring the specific gravity are:

  • Weigh the mineral in air (Wa).
  • Weigh the mineral in water (Ww).
  • Use the following equation:

Wa / ( Wa - Ww )

The resulting number is the specific gravity.
*Note that the specific gravity is a ratio- there are no units.

Image copyrighted - from the "Photographic Guide to Mineral Species CD" - used with permission.