Sapphire arises from the mineral corundum. When corundum is red, it is called Ruby, while all other colors are called Sapphire. It is mined in Thailand, Australia, China, Kenya, Tanzania, Nigeria, Sri Lanka and the USA, among others. Its color is determined by the temperatures and elements that affect the gemstone when it is formed underground. When measuring the hardness of a gemstone, you use the Mohs Hardness Scale. The scale varies from 1-10, where 10 is the hardest - here lies the diamond, which is the hardest gemstone. Sapphire is 9 on the Mohs Hardness Scale.