Sapphire can refer to either a gemstone or a specific type of crystalline material commonly used in various industrial applications.
Gemstone:
Natural sapphire: A natural sapphire is a precious gemstone belonging to the corundum mineral family. Corundum is an aluminum oxide mineral that, when it contains traces of chromium, iron, titanium, or other elements, exhibits a range of colors. Blue is the most traditional and prized color for sapphires, but they can also be found in various hues, excluding red (red corundum is classified as a ruby).
Synthetic sapphire: Due to its hardness and durability, synthetic sapphire is also created for use as a gemstone. These lab-grown sapphires share similar physical and chemical properties with natural sapphires.
Crystalline Material:
Aluminum oxide (Al2O3): In industrial contexts, sapphire often refers to a specific crystalline form of aluminum oxide. Sapphire is a hard and transparent material that possesses excellent optical and mechanical properties. It is widely used in the manufacturing of windows, lenses, watch crystals, and other optical components due to its scratch resistance and high transparency in the visible, ultraviolet, and infrared spectra.