or Specific Gravity, is a bulk property
of a material. Specific Gravity is the ratio
expressing the weight of a mineral compared
to that of an equal volume of water at 4°
C. So, a specific gravity of 3 means that,
at 4° C, one cubic centimeter of the material
weighs 3 times as much as one cubic centimeter
is a useful measurement in gem identification.
However, the density of a particular mineral
may vary greatly, even within a single crystal,
due to the presence of impurities, cracks
or bubbles. The density of a mineral can
be affected by several factors, including
chemical composition and crystal structure.
For example, Diamond and graphite are both
crystalline forms of the element carbon.
Diamond has a density of 3.5 because the
carbon atoms are tightly packed together
in the structure. Graphite on the other
hand, has a looser, more open structure
and has a density of only 2.2.