Though both stones are varieties of Corundum, in nature, Rubies are rarer than Sapphires. Both gems form under high temperature and pressure when fluid produced by magma interacts with silica and other rocks within the earth’s crust.
Corundum’s crystal structure is hexagonal and though Ruby and Sapphire are both aluminum oxides, trace elements like iron, vanadium and titanium are ultimately responsible for their color. Rubies are red because of the presence of chromium, and only red Corundum is known as Ruby. Any other color of Corundum is called Sapphire.
Burmese rubies are the most rare and among the most expensive gemstones in the world. Burmese ruby sets the international standard of quality and color for the gemstone. Relative to other gems, natural Ruby has always been a rarity, and the stone has been has been the world’s most valued gem for thousands of years.
Classic Burmese stones with ideal color – a vibrant and highly intense purplish red – have adorned the jewelry and treasures of royalty for centuries. Some Ruby mining records from Burma date back nearly 500 years and in early history, the stone was regarded as the most precious of the original twelve created by God. Today, due to a volatile political climate, very little new Burmese material is available, with many rare or old-stock Burmese stones only available by private sale to very wealthy collectors.
Worldwide, the highest quality deposits are found in Burma, Cambodia, Kenya, Tanzania, Thailand, and Vietnam, with additional Ruby deposits in Afghanistan, Colombia, Greenland, India, Pakistan, and the US. Recently, the discovery of Ruby in east Africa, especially in Madagascar, Mozambique and Tanzania has provided large quantities of high quality stones.
Rubies are never common, and natural, clean stones are extremely rare. Rubies and Sapphires are often heat-treated, and this permanent enhancement process can improve the color or transparency of many stones. Some Rubies display asterism – a phenomenon that is caused by inclusions of parallel fibers in the stone. When oriented correctly before cutting, these “Star” Rubies may show four, six, or twelve-rayed stars.
Ruby is the July birthstone, and the stone for Leo – a sign of the Zodiac ruled by the Sun. Ruby is thought to symbolize the power of love, strength and dominance, and has been called “The Queen of stones, and the stone of Kings.”