We have all heard how diamond is the hardest substance known to man. That is true, though Marvel Comics and Wolverine may want us to believe otherwise. So how can the hardest substance break?

The issue is that most people confuse hardness with durability. Hardness measured using the Mohs scale is a test that shows which substance can scratch another substance. When you here that diamond is a 10 on the scale, this is the Mohs scale. Diamonds can scratch glass but glass which is further down on the Mohs hardness scale cannot scratch a diamond.

The relative hardness says nothing about the durability of the substance, but rather , that it is hard enough not to be scratched by a softer material. How can a hard substance break by hitting a softer substance?

Every gemstone has what we call a grain or growth plain. Other terms used are matrices or even cleavage lines. These are effectively all the same term for a “place to break”. It is the way the crystal grows in nature. Some of the growth grains result in a pattern that makes the gemstone prone to breaking, fracturing or chipping. Diamonds have a grain that tends to make them slightly brittle. If a person hits the diamond just right on a growth plain, the diamond will break or chip. It is essentially like hitting a piece of wood on the grain. If you have ever chopped wood you know that hitting the log down the grain produces great splits, not so against the grain.

While diamonds are durable, they can break when hit hard enough on just the right angle. Sometimes it may seem like a small hit and other times it has to be extremely hard. It depends on the crystal formation of the diamond and the orientation of these features when the diamond is being cut and polished.

Some gemstones that are softer on the Mohs scale are in fact more resistant to chipping and cracking than diamond.

From what we have seen in our store, over the years, diamonds are amazingly resistant to breaking. However, just know that they can. And for those people that hear the urban myth that hitting a diamond with a hammer won’t break it, don’t try it unless you have lots of money to burn! When hit with a hammer, a diamond will break for sure.