A Ruby is a pink to blood-red gemstone.
Its name comes from ruber in latin that means red.
Prices of rubies are primarily determined by color and its luster is Vitreous.
Generally, gemstone-quality corundum in all shades of red, including pink, are called rubies.
However, in the United States, a minimum color saturation must be met to be called a ruby, otherwise the stone will be called a Pink Sapphire.
Diamonds are graded using criteria that have become known as the four Cs, namely color, cut, clarity and carat weight.
Similarly natural rubies can be evaluated using the four Cs together with their size and geographic origin.
It's formula is Al2O3:Cr