Among gemstones the ruby is considered to be the most powerful and is associated with the astrological signs, Leo, Scorpio and Cancer.
Prior to 1800 all red gemstones were thought to be rubies, many have since been found to be spinel or garnet. Rubies are from the Corundum mineral family and are the red variety of that family, other colors being sapphires, thus all rubies are sapphires but only red sapphires are rubies.
Corundum are notable for their hardness and rubies have a Mohs scale hardness rating of 9 making them one of the hardest gemstones, only moissanite and diamond are harder. Corundum can be literally defined as ruby, the origins of the name coming from the Sanskrit word kuruvinda and the Tamil word kuruntam.
Some famous rubies include the 137 carat Rosser Reeves Star Ruby, the 100 carat Edith Haggin de Long Star Ruby, the 167 carat Edward Ruby.There is also the Peace Ruby that upon discovery was 43 carats, cut to a finished 24 carats. The Peace Ruby, another interesting ruby, was unearthed in the Mogok valley on June 30, 1919 and gained it's name because it was discovered two days after signing of the Treaty of Versailles on June 28, 1919 at the end of World War I.
Metaphysically rubies are said to be able to reduce negative thoughts, bring love of self and of spirit, and inspire courage, confidence and loyalty. People who own or wear rubies are said to be peaceful and content and rubies are notably given as gifts in friendship.
Rubies are also very prominent in religious history as well as Greek mythology.