size: 5 weight: 8.2 grams material: 90% platinum gemstones: natural australian semi crystal opal 5.06ct 17 x 11mm 0.26ctw of natural Si clarity, g-h diamonds Notes from the Curator Semi-crystal opal occupies the middle ground between fully transparent crystal opal and opaque varieties—the designation refers to translucency that allows light to glow through the stone without complete clarity. That transparency permits light to pass through the gem, creating a luminous, layered effect that gives the play-of-colour remarkable depth and dimension, and at 17 × 11 millimetres this 5.06-carat oval cabochon is sized above the typical commercial run. The three-stone format—here a central opal flanked by two smaller diamonds—was codified in the late Victorian era and widely marketed as a symbol of past, present and future, though the configuration has ancient roots. Platinum's neutral lustre has made it the metal of choice for opal mounting since the early twentieth century, when jewellers realised that crystal opals face-up more brilliantly against a dark background, which enhances the play-of-colour. The Romans believed opal to be the symbol of hope and called it cupid paederos—"the child as beautiful as love"—and considered the wearer safe from disease, an attribution that survived in European courts for nearly a millennium.