Corundum (var Ruby) is a variety of Corundum. Corundum is most recognized for its two famous gem varieties, Ruby and Sapphire. Ruby and Sapphire are chemically the same mineral, but simply differ in color, with Ruby being the red variety, and Sapphire the variety that encompasses all other colors (although blue is the most popular and desired color). Ruby is pink-red to blood red, has a vitreous to adamantine (brilliant, diamond-like) luster, and can be transparent to opaque, with transparent crystals the most desirable and commanding the greatest price. Ruby is one of the top four popular gemstones in the world (Diamond, Sapphire, Ruby and Emerald) due to its beauty, intense red color and extreme durability; it is 9 on the Moh’s hardness scale, only surpassed by Diamond, 10.

The crystal system for Corundum (var Ruby) is hexagonal, primarily hexagonal prismatic, steep dipyramidal, tabular and rhombohedral. Other forms include granular, massive and striated.

Localities for quality specimens of Corundum (var Ruby) include Afghanistan, Australia, Brazil, Columbia, Madagascar, Myanmar, Namibia, Tanzania and Thailand.