Ruby is a pink to the blood-red colored gemstone, a variety of the mineral corundum (aluminum oxide). Other varieties of gem-quality corundum are called sapphires. Ruby gemstone is one of the traditional cardinal gems, together with amethyst, sapphire, emerald, and diamond. The world's most valuable ruby gemstone is the Sunrise Ruby gemstone. Shop any of our ruby loose gems now and even customize any 18K Engagement Ring/Pendants/Earrings etc.