Natural Australian Boulder Opal Rub, Freeform, Ring STone w/Amazing Color, 4.9ct. This one-of-a-kind opal stone would make a great addition to your opal collection or further process into a luxurious piece of jewelry. Please see photos and video for details and condition. Add 3.99 shipping via USPS. Combined Shipping is $1.00 for additional mineral or gemstone specimens.