Durability is a gem's ability to resist scratching, breaking, and damage from heat, light or chemicals. It has three parts: hardness, toughness and stability.
In more detail
A gem can be strong in one part and weak in another. Diamond is the hardest gem, but it can cleave. Emerald is 7.5 to 8 on the Mohs scale, but its toughness is only fair to good. Corundum is hard, has excellent toughness and is stable in normal wear.
Related terms
- Hardness (Mohs): Hardness is a gem's resistance to scratching. Gemologists rank it on the Mohs scale, on which diamond is 10.
- Toughness: Toughness is a gem's resistance to chipping and breaking. It differs from hardness, which is resistance to scratching.
- Stability: Stability is a gem's resistance to damage from heat, light and chemicals.
- Cleavage: Cleavage is a mineral's tendency to split along flat planes in its crystal structure. A hard knock in a cleavage direction can split a stone.
- Mohs scale: The Mohs scale ranks minerals from 1 to 10 by which can scratch which. Diamond is 10 and corundum is 9.