Rubies are prized for their deep red color, caused by trace amounts of chromium. In ancient India, rubies were considered "ratnaraj," meaning "king of precious stones." The Mogok Valley in Myanmar, known as the "Valley of Rubies," has produced some of the world's finest specimens for centuries. Interestingly, rubies and sapphires are both forms of the mineral corundum, with their different colors resulting from varying impurities.
