The mineral known for its hardness and commonly used in jewelry is diamond. Diamonds score a perfect 10 on the Mohs scale of mineral hardness, which measures the scratch resistance of various minerals. Due to their exceptional hardness, diamonds are ideal for engagement rings and other fine jewelry, symbolizing lasting love and durability. They also have a unique refractive quality, which contributes to their brilliance and sparkle. Additionally, diamonds come in various colors, which can enhance their value and appeal. Their beauty and toughness make them a sought-after gemstone in various cultures worldwide.