The primary component of diamonds is carbon. Diamonds are formed under high-pressure and high-temperature conditions deep within the Earth's mantle. Carbon atoms bond in a crystal structure, creating the unique properties that make diamonds exceptionally hard. This crystalline arrangement also contributes to their brilliant optical qualities, allowing them to refract light and sparkle. Diamonds can occur naturally or be synthesized in laboratories. Due to their hardness, they are not only prized as gemstones in jewelry but also have industrial applications, such as cutting and grinding tools.