A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. Ruby is considered one of the four precious stones, together with sapphire, emerald and diamond.
The fiery and captivating Ruby is a stone of nobility, considered the most magnificent of all gems, the queen of stones and the stone of kings. Ancients believed it surpassed all other precious stones in virtue, and its value exceeded even that of the Diamond. The Chinese Emperor Kublai Khan was said to have offered an entire city in exchange for a sizable Ruby.