Opal

About Opal

Their play of color comes from microscopic silica spheres that diffract light - each opal contains millions. Australia produces 95% of the worlds precious opals. They contain 3-20% water. The Olympic Australis opal weighs 17,000 carats. Lightning Ridge produces the famous black opal. Ancient Romans considered them the most precious of all gems. They can craze (develop cracks) if they dry out. Fire opals from Mexico are orange-red without play of color. The Welo opal from Ethiopia can exhibit vivid patterns. NASA discovered opal deposits on Mars. They have been considered both lucky and unlucky throughout history.