Boulder opal grows as thin seams of precious opal within Queensland ironstone; cutters keep the host rock as a natural backing, creating dramatic scenes where fire flashes against warm brown matrix. Each stone is literally a landscape — and structurally tougher than solid opal of equal thinness.GEMIC Institute’s boulder opals are natural Australian stones, filmed individually to show their play-of-color, and certified by our Siem Reap laboratory. Strictly one of a kind; worldwide tracked shipping, 30-day inspection.