Updated: Sep 2, 2019
Sapphires are a form of corundum, the second-hardest mineral. Commonly ranging in color from light to dark blue, they are found chiefly in placer deposits.
When people say “sapphire,” they’re usually referring to the royal blue variety of this gem, although it can occur in all colors of the rainbow (except red, which is classified as ruby instead).
The September birthstone, sapphire, was once thought to guard against evil and poisoning. It was believed that a venomous snake would die if placed in a vessel made of sapphire. Traditionally a favorite stone of priests and kings, the sapphire symbolizes purity and wisdom.