Along with diamonds, emeralds and sapphires, rubies are known as one of the four precious stones.
With a hardness of 9.0 on the Mohs scale rubies are one of the hardest gemstones. Only diamonds and moissanite of the natural gemstones are harder, with diamonds having a hardness of 10.0.
Ruby, the king of precious gems, is the birthstone for fortunate folks born in July. Symbolic of the passion and energy associated with the color red, the vibrant ruby is said to bring love and success.