The mineral corundum goes by a few different names. The red variety is called ruby, and every other color is called sapphire. 

The Bible considers the ruby to be the most precious of gemstones, as is evinced in Proverbs 31:10: "Who can find a virtuous woman? for her price is far above rubies."

The Indians believed those who donated rubies to honor Krishna were assured being reborn as an emperor in a future life. In China, the Mandarin's rank was indicated by the color of the ruby in his ring. They have been prized for millennia in nearly every culture.

The color red is representative of our most powerful emotions, love and anger. As a symbol of passion, ruby makes for an ideal romantic gift, and because it's second to diamond in hardness, rubies make excellent stones for engagement rings due to their durability.