Judging by what celebrities wear on the red carpet, luxury cocktail rings continue to reign supreme. If you’re looking to bring some sparkle to your favorite Valentine, consider giving her (or him?) a ring with gems of grand proportions, one that’s a fashion statement and a work of art. But be warned: while these jumbo rings dazzle on the red carpet, only some may be suitable for everyday wear.

Diamonds are known for being one of the hardest substances on earth. A diamond is so hard it ranks as a 10 on the Mohs scale–the highest level of hardness. But what is the Mohs scale?