Cleavage and Fracture


Cleavage and Fracture of Gemstones

Cleavage is the splitting of gems and minerals along one of the planes related to the stone's structure. Crystalline minerals have cleavage and fracture, whereas amorphous or massive stones only fracture.

Depending on the ease with which a crystal can be cleaved, one differentiates between perfect (euclase), a good (Sphene) and imperfect cleavage (peridot). Some gemstones cannot be cleaved at all (quartz). A loosing of contact twins is not called cleavage, but separation or parting

Cleavage is considered perfect or if the stone parts and produces perfect smooth planes (diamond, topaz) and is very important in the diamond - cutting.

Cleavage is used to divide large gem crystals or remove faulty pieces. Today, small pieces are usually sawn in order to avoid unwanted cleavage, and to make the best use of the shape of the stones

The breaking of a gemstone with a blow producing irregular surface is called fracture.

Fracture is the way a stone breaks. Consider fracture to be similar to a piece of wood breaking in a direction other than the direction of it's grain. Conchoidal fracture, which is most common in gemstones, shows a series of arcs that spread outward.

Fracture can be conchoidal (shell-like), uneven, smooth, fibrous, splintery or grainy


When a gemstone breaks along a surface that is not related to its internal atomic structure, it is said to fracture.