We’ve all heard the old saying “A diamond is forever.” Forever is an overstatement but since diamonds are extremely hard and do resist any kind of scratching, this would be a likely assumption. Diamonds will often break, given the right circumstances. How could an extremely hard substance break? It’s so hard that it’s brittle. Actually diamond’s toughness is rated “good” (not “excellent” like the gemstone jade). Remember that there is a significant difference between hardness and toughness. Hardness is simply the resistance to scratching and toughness is the resistance to breakage, to powdering or to flattening under repeated pounding