This Reddit Thread Is Here to Set Straight Common Beliefs That Are Misconceptions

Both diamonds and coal are made of carbon, but they’re different products. Placement within the earth aside, coal has too many impurities to ever become diamond. Both rubies and sapphires are made from corundum and are only second to diamonds in hardness. Emeralds come from mineral beryl and are much less hard.

The only other gemstone that falls in the top hardness scale category is moissanite, often used as an alternative to diamonds in jewelry. It’s usually clear with a yellowish tint and very affordable, casting rainbow refraction instead of the pure white that diamonds offer.