What is cleave in gemology?

In gemology, cleave refers specifically to the phenomenon that occurs when a gemstone breaks along a smooth, flat surface that is parallel to planes of atomic weakness within the crystal structure. This is a natural occurrence related to the internal arrangement of atoms in the mineral, and it reflects the inherent characteristics of the material. Cleavage planes are a result of weaker atomic bonding along certain directions, making it easier for the stone to break consistently along those lines.

The presence of cleavage in a gemstone can significantly affect its durability and how it can be shaped or polished. Understanding the concept of cleavage is crucial for gemologists as it can influence both the aesthetics and the structural integrity of the finished gemstone, guiding decisions during the cutting and shaping processes.