It measures a stone's resistance to breaking, chipping, and cracking. Gemstone toughness and hardness are not the same things. Toughness is the stone's ability to bear physical pressure, whereas hardness is related to the stone's ability to withstand scratching. There are six levels of gemstone toughness: extraordinary, outstanding, good, fair, bad, or fragile. Another aspect to consider in this case is gem cleavage. It speaks to the stone's capacity to fracture along particular planes. If the atomic bonds are weaker, certain planes inside the crystal structure will break. It is a crucial component to take into account when trimming. For example, lapidaries must use extreme caution when cutting natural emeralds because of their brittle nature.
