What is a fracture of a mineral?
In order to understand this, you need to understand that there are two basic ways in which a mineral can break. The first way is via cleavage. Cleavage is a tendency to break along flat surfaces. Cleavage is cause by planes of weakness within the actual molecular structure of the mineral crystals. The other way in which a mineral can break is called fracture. Fracture is a tendency to break along uneven surfaces. This occurs when the mineral breaks in a direction for which there are no planes of weakness in its structure.
