The September birthstone is usually thought of as the blue gem variety of corundum, but it comes in all the colors (pink, orange, yellow, green, purple, black, and colorless) except red (ruby). Light red, pink, and violet are usually called sapphires. The coloring in blue gems is due to iron and titanium. Sapphire comes from the Greek word sappheiros for blue. It is the second hardest gemstone after diamond. It is also the gem for celebrating the 5th and 45th wedding anniversaries.