Ruby is distinguished for its bright red colour, being the most famed and fabled red gemstone. It is a most desirable gem due to its hardness, durability, luster, and rarity. Ruby is the red variety of the mineral Corundum. Sapphire, the other gem variety of Corundum, encompasses all colours of Corundum aside from red. In essence, Ruby is a red Sapphire, since Ruby and Sapphire are identical in all properties except for colour. However, because of the special allure and historical significance, Ruby has always been classified as an individual gemstone.

The colour of Ruby ranges from bright red to dark reddish-brown. The most preferred colour is a deep blood red with a slightly bluish hue. Such Ruby is known as "Burmese Ruby". Ruby from Burma (now Myanmar) is famous for its exceptional coloring.

The colour of a ruby is the most important feature. Its transparency is only of secondary importance. So inclusions do not impair the quality of a ruby unless they decrease the transparency of the stone or are located right in the centre of its table. On the contrary: inclusions within a ruby could be said to be its 'fingerprint', a statement of its individuality and at the same time, proof of its genuineness and natural origin.