Ruby

Ruby is red corundum, all other varieties of corundum being referred to as sapphire. Corundum is the second hardest substance on the Mohs scale, with a rating of 9. It is this combination of excellent hardness and the rich color and silky shine that make fine ruby gems so valuable.
Rubies range in color from pinkish to orangey and purplish and brownish red, depending on the chromium and iron content of the stone. Most experts expect a medium to medium-dark color tone in a very good ruby gemstone.
The traditional sources for fine rubies are Burma and Thailand. Today we also find many affordable rubies coming from Africa and Madagascar