Opal Engagement Rings Australia

Opal is amorphous silica with water trapped in microscopic spheres. When those spheres are uniform in size and packed in a regular grid, they diffract light into spectral colours, giving precious opal its play of colour. Common opal does not show this effect. Australia produces over 90 per cent of the world's precious opal.

Body colour can be white, grey, black, crystal (transparent) or fire (warm orange to red). Play of colour can flash green, blue, red, orange and violet. Black opal with vivid red and green play of colour is the most valuable. Fine boulder opal shows colour on a natural ironstone backing. Crystal opal is transparent with internal flashes that seem to float inside the stone.

Opal is 5.5 to 6.5 on the Mohs scale, which is closer to glass than to sapphire. It can scratch and chip more easily than the precious stones. The water content also means opal can crack ("craze") if exposed to dry air, sudden temperature changes or prolonged heat. Not a strong choice for an engagement ring worn through every kind of activity. A bezel setting and careful habits help.

Body tone (the lighter or darker base) and brightness of play of colour are the main value drivers. Larger, brighter patterns like broad flash and harlequin are worth more than smaller pinfire patterns. Solid opals are worth more than doublets (a thin opal slice on a backing) and triplets (opal sliced between a backing and a clear cap), though doublets and triplets bring the look at a much lower price.

Solid opal is typically untreated. Smoke and sugar treatments are sometimes used on lower-grade Ethiopian opal to deepen body colour. Doublets and triplets are constructed rather than treated. Lightning Ridge in NSW produces the world's finest black opal. Coober Pedy in SA is known for white opal. Queensland produces boulder opal. Ethiopia has emerged as a major source of hydrophane opal that absorbs water.

Best as pendants, earrings and dress rings worn for occasions. Bezel-set boulder opal rings are tougher than crystal or black opal in claw settings. Australian black opal makes a striking, once-off engagement ring for someone who understands the trade-offs and is prepared to handle the stone carefully.

Clean only with a soft, slightly damp cloth. Never use ultrasonic or steam cleaners. Avoid sudden temperature changes, prolonged dry air, strong sunlight and any harsh chemicals. Store wrapped in a soft cloth in a sealed container. Remove opal rings before housework, exercise and dishwashing.

Fine black opal from Lightning Ridge with vivid red play of colour can rival diamond per carat. White opal, crystal opal and boulder opal sit at far more accessible prices. Doublets and triplets offer the look at a fraction of the cost of solid opal.