Ruby is red corundum, all the other color varieties of the corundum are called Sapphire. Corundum is the second hardest substance on the Mohs scale, with a rating of 9. Diamond tops the scale with a rating of 10. Ruby is named after the Latin word "ruber" for red. Ruby is one of the most expensive gems, large rubies being rarer than comparable diamonds.
Ruby is the birthstone f...or those who are born in July. Ruby is also used to celebrate a couple's 15th and 40th anniversary.
Rubies range in color from pinkish to orangey and purplish to brownish red, depending on the chromium and iron content of the stone. The most desirable color is the so-called "pigeon's blood", a pure red with a hint of blue. Color is the most important consideration, with clarity a distant second. Lighter red to pink rubies are commonly called Pink Sapphire.