A Belle Epoque opal and diamond brooch, circa 1915, the oval-shaped crystal opal cabochon, measuring approximately 23.0 mm x 18.2 mm x 5.8 mm, displaying exceptional play-of-colour of all spectral colours, set within a ribbon and floral garland surround, mounted throughout with millegrain single-cut diamonds, to the bow surmount, centring an old brilliant-cut diamond collet, opal weighs approximately 13.80 carats, diamonds approximately 0.70 carat total, mounted in platinum and gold, length 5.5 cm, width 3.5 cm