Prices of rubies are primarily determined by color. The brightest and most valuable “red” called pigeon blood-red, commands a huge premium over other rubies of similar quality. After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions will indicate that the stone has been treated. Cut and carat (size) also determine the price.
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.
Of the world’s rubies, the finest are found in Myanmar (Burma). Burmese gems are prized for their hue and high degree of saturation. Thailand buys the majority of Myanmar’s gems. Myanmar’s “Valley of Rubies“, the mountainous Mogok area, 200 km (125 miles) north of Mandalay, is noted for its rare pigeon’s blood rubies and blue sapphires. Working conditions in the Mogok Valley are primitive and as such similar to mining conditions in other parts of the world.