Geology Reference
In-Depth Information
sample you hold in your hand. For example, the mineral pyrite appears gold but
leaves a black streak when rubbed across a streak plate.
Measuring mineral strength
Other physical characteristics useful for identifying minerals indicate the strength of the
crystal structure. These include hardness, tenacity, cleavage, and fracture.
Hardness
Mineral hardness is the most useful way of identifying minerals.
Hardness
is how well a
mineral resists being scratched. When you scratch the surface of a mineral you are
breaking the bonds between atoms, so hardness is a way of measuring how strong those
bonds are.
Mineral hardness is given a value on
Mohs scale of relative hardness,
which is illustrated
in Figure 6-2. Mohs scale, named after the mineralogist Friedrich Mohs who developed it,
is a
relative scale,
which means it ranks the minerals in relation to one another — not
along an absolute measure of hardness.
Figure 6-2:
Mohs
relative mineral
hardness scale.
