Sapphire

Sapphire is one of the most celebrated precious gemstones in the world and like Ruby, it's a variety of corundum, one of the hardest minerals on earth at Mohs 9. While most people think of sapphire as blue, natural "fancy" sapphires occur in yellow, purple, orange and green too — the only color corundum can't be is red, because that's what makes it a Ruby. The color comes from trace amounts of iron, titanium, chromium, vanadium or magnesium in the crystal. Sapphire is the state gemstone of Montana and one of September's birthstones.