Ruby
Ruby is the most valuable variety of the corundum mineral species, which also includes sapphire. Traces of chromium give this red variety of the mineral corundum its rich colour. Long valued by humans of many cultures. In ancient Sanskrit, ruby was called ratnaraj, or “king of precious stones.”
Birthstones & Anniversaries
Ruby is the birthstone for July and the gem for the 15th and 40th anniversaries.
Facts
Mineral: Corundum
Chemical composition: Al2O3
Colour: Red
Refractive index: 1.762 to 1.770
Birefringence: 0.008 to 0.010
Specific gravity: 4.00 (+/- 0.05)
Mohs Hardness: 9
