The International Gem Society gives this example on Hardness & Toughness:
- Did you know the particles of dust you see floating in the air and settling on tables are mostly silicon quartz? Their hardness on the Mohs scale is around 7 to 7.5. That means those particles can remove the finish from your car, the polish from your table, and actually cut glass. Dust and other everyday hazards make gemstone hardness an important consideration when designing and wearing jewelry.
- You may know that diamond, with a hardness of 10, is the hardest material in the gem world. However, there’s an old saying among gemologists: “If you hit a diamond with a hammer, it’ll shatter into a dozen pieces.
- If you hit a piece of quartz with a hammer, it’ll split in two. If you hit a piece of jade with a hammer, it’ll ring like a bell!” How is that possible if diamond is the hardest gem? What Does Gemstone Hardness Mean? Gemstone hardness is a very misunderstood property.
- The word “hardness” has a very specific scientific meaning in gemology that differs considerably from its everyday usage.
- The scientific definition of hardness is the ability to resist scratching, nothing more.
What is the Take-away from this Example?
Just because Diamonds are rated among the hardest surfaces known to man, this does not mean that they are the toughest structurally. A high MOHS rating does not guarantee Toughness.
For example, diamond is harder than a steel hammer. You can cut through a hammer with a diamond. However, You smash that same diamond with a hammer.
Diamond is the hardest Gem at 10, followed by Moissanite at 9.12-9.17, Corundum at 9, Benzgem Simulated Diamonds at 8.50 then all other Precious and Semi-Precious Gemstones, in descending order.