A ruby is a precious red gemstone made of the mineral corundum, celebrated for its brilliant crimson color and exceptional durability. 

Physical and Chemical Properties

• Composition: Formed of aluminum oxide (Al₂O₃), where chromium replaces a small fraction of aluminum atoms to create the red hue.

• Hardness: Rates a massive 9 on the Mohs Mineral Hardness Scale, making it the second-hardest natural mineral after diamond.

• Luster: Exhibits a brilliant vitreous (glass-like) to subadamantine shine.

        Inclusions: Natural rubies commonly feature needle-like rutile                       inclusions known as "silk," which help gemologists distinguish natural             stones from synthetics.