When a mineral cleaves, it often exhibits many cleavage surfaces, but most of these are generally parallel to one another. A hundred cleavage surfaces parallel to one another all define a single direction of cleavage, because all of them are parallel to the same zone of bond weakness. It is the number of directions of cleavage that we record, along with the angles between them. Minerals with two or more cleavage directions generally have a "stair-step" appearance when viewed with a magnifying glass. A mineral with two directions of cleavage may indeed be broken in some other direction-by irregular fracture. Thus, a single specimen may exhibit smooth cleavage planes in some directions, and irregular breakage surfaces in others. The more breakage surfaces we can see, the more clues we have to the mineral's internal structure.

It may be difficult for the beginner to distinguish between cleavage and crystal faces. After all, both are smooth, planar surfaces. Two hints will help make the distinction easy. (1) If a mineral's outer surface shows a tarnish or alteration, the crystal faces will be tarnished or dull; if cleavage planes are present, they are usually recently made and will be fresher and less altered. (2) If many surfaces are present parallel to one another, they are most likely cleavage surfaces.