When a mineral breaks it can be in an irregular manner - fracture or it
can split along well defined surfaces - cleavage.
Cleavage is used to distinguish between minerals of similar hardness, colour form etc.
On a basic level, cleavage is described by giving the number of planes of
cleavage and the quality of the cleavage plane:
Perfect, good, fair, poor, none.

Cleavage is not used as a means to identify minerals in this application

I have included some summary tables for the minerals which provide information about cleavage using crystallography terms for the directions of the cleavage.
eg {100} perfect. An explanation of this is beyond the scope of what I intended for these pages. Refer to a good mineralogy or crystallography book. I will include links to some sites later.