Sapphire is a precious gemstone which is typically blue, but natural 'fancy' sapphires also occur in yellow, purple, orange, and green colors. They occur also in gray and black, and can be colorless.
Sapphires are hard stone at 9 Mohs, making them perfectly suitable for rings, engagement rings, earrings, pendants, or any other jewelries used everyday.
It is common practice to heat natural sapphire to improve or enhance color. Evidences shown that the practice goes back at least to Roman times. Now, heat treatment often accompanied by beryllium under very high heat (just below the melting point of sapphire).
Be aware when you found a sapphire gemstone that is very, very, cheap. The saying, 'if it is too good to be true, then probably it is not true" applies here. They are typically very clean without any inclusions. Visit only your trusted store to ensure you get genuine sapphire.