Sapphires are typically blue gemstones that can also appear yellow, green, purple or orange. These gemstones are made of corundum and are mined across the world in many countries including the United States, Australia, China, Madagascar and India. Sapphires are usually valued based on the quality of their blue hue, but they can occur in other colours and can even be completely colourless. The blue hue in typical Sapphires is due to how the light going through the crystal interacts with the atomic structure, and this is why the blue colour of a Sapphire is used to figure out how valuable it is. Sapphires are most often used in jewellery, and clear varieties can be used as a cheaper alternative for diamonds