Corundum

Corundum is known for its exceptional hardness and durability, second only to diamond.

Part of speech: noun
Definition: Corundum is a crystalline form of aluminum oxide and is naturally clear, but can have various colors depending on impurities. It is highly prized in the jewelry industry as the minerals ruby and sapphire are varieties of corundum, distinguished by their color - red for ruby and blue for sapphire, though sapphire can come in other colors as well. The hardness of 9 on the Mohs scale makes corundum an excellent choice for jewelry that requires durability and long-lasting wear. Beyond its use in jewelry, corundum is also valued for industrial applications such as in abrasives and watches due to its scratch resistance and stability.