Cleavage minerals examples

Overview

As minerals are broken (such as with a rock hammer, for example), some may cleave, or break, along smooth flat planes known as cleavage. These flat surfaces are parallel to directions of weakness within the crystal.

All the bonds among the atoms within a mineral may not be of the same strength so that when a mineral is broken, it breaks along these zones of weakness. This results in flat cleavage planes. Minerals with perfect cleavage break along a smooth, flat plane, while those with poor cleavage break in a more irregular fashion.

Some minerals do not contain zones of weakness either because all of the bonds are the same strength or the weaker bonds are not aligned within a plane.

Halite cleavage

If this is the case it will not have cleavage, but rather breaks in a random and irregular fashion. Make sure to distinguish cleavage from crystal form. Crystal form occurs as a mineral grows, while cleavage only forms as a mineral breaks.

See Figure 7.10 for the main types of cleavage and an example of each.

A mineral may have one or more cleavage

how to identify cleavage planes in minerals

example of cleavage in minerals