Cleavage and Fracture

Cleavage

If minerals and gemstones are struck with a hammer or exposed to pressure, they may split along their weakest planes, or surfaces. This is called cleavage and the extent of cleavage varies from mineral to mineral. Their are four types of cleavage:

1. perfect
2. distinct
3. indistinct
4. non-existent

Fracture

As with cleavage, if a mineral is hit with a heavy object, it may break up. This is called fracture and it is variously described as:

1. uneven
2. conchoidal(shell like)
3. splintery
4. hackly(with jagged irregular surfaces)

Most minerals fracture and cleave, but some only fracture.

Back to previous page