Sapphire is the non-red variety of corundum (the red variety of corundum is ruby). Sapphires with inclusions of tiny, rutile needles exhibit an optical property called asterism. This is the star shaped effect seen in star sapphires and is usually only seen in cabochon cuts. Star sapphires usually have six ray stars..

Blue is the most popular color for sapphires, but they can be almost any color, including yellow, green, white, colorless, pink, orange, brown, and purple.

Mining locations for sapphires include Myanmar, Madagascar, Sri Lanka, Australia, Thailand, India, Pakistan, Afghanistan, Tanzania, Kenya and China.