Ruby is noted by its deep red color and is the official birthstone of July. It is also used for the 15th and 40th wedding anniversary.
Rubies can have the highest per carat price of almost any gemstone making it one of them most valuable in the color stone market. Sapphire is a color variant of the same mineral, corundum. In May, 2012 a 25.59 carat ruby ring sold for over $32 million. That is over $1.2 million per carat, setting a new record for any colored gemstone. It is second in hardness to diamond.
Ratnaraj, the Sanskrit word for Ruby is translated as "king of the gems" and was prized by ancient Hindus. Royalty families would use Ruby to ward evil. It was believed that Ruby would get darker in the presence of evil and become light when evil was gone. This would supposedly work only if possessed by the true owner of the Ruby.
Mineral Group: Corundum
Refractive Index: 1.762 to 1.770
Birefringence: 0.008 to 0.010
Specific Gravity: 4.00 (+/- 0.05)
Mohs Hardness: 9