Rubies are supposed to signify passion and sexual love. The name comes from the Latin word rubens which means red. They come from the corundum family of gemstones. Red corundums are called rubies, blue corundums are called sapphires.
They've been prized for thousands of years due to the colour and hardness of the stone (only diamonds are harder). The best rubies are found in Asia (north Burma, Thailand and Vietnam). Burmese warriors used to wear them into battle believing the redness and hardness of the stone protected them..
Like the birthstones for April and May, this birthstone is one of the more expensive ones.