Sapphire
Sapphire is the non-red variety of corundum, the second hardest natural mineral known to mankind. The red variety of corundum is Ruby. White (or colourless) sapphire would more properly be called corundum. The blue color is by far the most popular color for sapphire but it also comes in orange-pink, golden, white, and even black.
Kings used to wear sapphire around their necks as a powerful defense against harm. The stone preserved the wearer from envy and attracted divine favor.
Sapphire represents truth, sincerity and consistency. Sapphire engagement rings are given to express commitment and loyalty.
Sapphire is used for clear thinking.