Rubies

Ruby and sapphire are the two varieties of the mineral corundum. Their exceptional hardness is surpassed only by diamonds. Red corundum is called ruby, and all other colors are called sapphire. The cut-off between ruby and pink sapphire on one end and plum sapphire on the other has long been a subject of controversy. Of course, gem dealers want the gem they're selling to be classified as a ruby because the name alone increases its value. Rubies are found in Thailand, Burma, Sri Lanka, Cambodia, Vietnam, Madagascar, Tanzania, Kenya.