The Science Behind the Play-of-Colour
No other gemstone moves like an opal. As light strikes the stone's surface and penetrates its silica structure, it diffracts through a lattice of microscopic spheres — each arranged in a regular pattern that breaks light into its component wavelengths, producing the rolling, shifting spectral display gemmologists call play-of-colour. The colour you see changes as the stone moves relative to the light source, which is why every opal appears almost alive in the hand.
This phenomenon is unique to opal — no other natural gemstone produces true play-of-colour — and it is why Australia's opal fields are among the most significant geological treasures on earth. The conditions required for gem-quality opal formation are extraordinarily specific: ancient shallow inland seas that deposited silica-rich water into sandstone or ironstone cavities, which then slowly hardened over millions of years into the precious mineraloid we know today.
Australia produces approximately 95% of the world's gem-quality opal. For clients along the NSW South Coast — from Kiama to Wollongong and the Southern Highlands — working with a local gemmologist like Sara to select and set an Australian opal is a way of connecting to something genuinely and extraordinarily from this country.
Sara has a curated selection of black, boulder, and white opals available for viewing by appointment in Kiama.
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A custom black opal and diamond statement ring — the dark body tone of the Lightning Ridge opal makes the play-of-colour appear to blaze with intensity.
Black, Boulder, and White — Understanding the Difference
Black opal, found almost exclusively at Lightning Ridge in north-western New South Wales, is the most prized and valuable variety. The dark body tone — ranging from dark grey to jet black — provides a dramatic background against which the play-of-colour appears vivid, intense, and brilliantly saturated. A top-quality Lightning Ridge black opal with strong red fire across its face is among the most spectacular and valuable gemstones in the world. Lightning Ridge is only a few hours inland from the NSW South Coast, making black opal an especially meaningful stone for Sara's clients in this region.
Boulder opal forms within ironstone host rock in Queensland's Quilpie and Yowah regions. Rather than being extracted from the host entirely, boulder opals are typically cut with a thin backing of the natural ironstone, which provides stability and — like black opal — a dark backing that intensifies colour. Each boulder opal is uniquely shaped by the natural formation of the host rock, making every stone a one-of-a-kind sculptural object.
White opal, produced mainly at Coober Pedy in South Australia, has a pale, milky body tone that displays play-of-colour in softer, more pastel hues. While white opals are less dramatic than their black counterparts, they suit certain jewellery styles beautifully — particularly when set in yellow gold, which warms their cool pastel fire into something luminous and feminine.
Left: A bespoke black opal and diamond pendant in 18ct yellow gold. Right: A repurposed white opal in a contemporary hinged bangle — both crafted in Sara's Kiama studio.
Setting Opals — An Art Requiring Special Skill
Working with opal requires a different approach to most gemstones. With a Mohs hardness of 5–6.5 and a sensitivity to sudden temperature changes (which can cause crazing — fine surface cracks), opals demand thoughtful design and specialist setting techniques. Sara selects protective settings — deep bezels, half-bezels, and beaded collet mounts — that shield the stone's edges while allowing light to enter freely across its face.
For custom opal jewellery, Sara begins by assessing the stone's individual character: the distribution and intensity of play-of-colour, the shape, and the body tone. These qualities determine the setting style, metal choice, and how the stone will be oriented in the finished piece. A black opal with red and orange fire suits a bold yellow gold setting; a delicate white opal with blue and green flash can be breathtaking in a fine diamond-studded white gold mount.
Opal remodelling is one of Sara's most requested services. Many clients arrive with beloved but dated opal pieces — perhaps a brooch from an estate, or a pendant whose gold has yellowed and worn — and work with Sara to transform the stone into something they will wear proudly every day. Sara handles the removal, assessment, and resetting of existing opals with the same care she brings to new stones, ensuring the gem's integrity is preserved throughout.
Sara's remodelling service breathes new life into treasured opals — transforming inherited stones into contemporary designs made for the next generation.
Debunking the "Bad Luck" Myth
The persistent belief that opals bring bad luck to non-October wearers is one of jewellery's most enduring myths — and one with a surprisingly specific origin. Sir Walter Scott's 1829 novel Anne of Geierstein featured a character whose enchanted opal changed colour with her moods and brought misfortune. The story was pure fiction, but it proved devastatingly effective: in the months following publication, opal sales across Europe reportedly collapsed by 50%, and prices fell dramatically.
The irony is that for most of human history, opals were considered extraordinarily lucky and powerfully protective. Ancient Romans prized them above almost all other gems, calling them opalus — "precious stone." Arab cultures believed opals fell from heaven in lightning flashes. In medieval Europe, opal was called the Patronus furum — "patron of thieves" — not because it brought bad luck, but because it was believed to make the wearer invisible. Aboriginal Australians — the traditional custodians of opal country — have long regarded the stone as sacred, associated with the Dreamtime.
The truth is simple: opals are one of nature's most extraordinary creations. They are Australia's national gemstone for a reason. Wear them in health, confidence, and joy.
