Is it just me, or are opals everywhere at the moment? Perhaps it’s because this year marks the centenary of the discovery of opals in Australia, by rebellious teenager Willie Hutchinson. As with most initial gem discoveries, it was entirely serendipitous. Willie went for a walk, when tasked with fetching water for the family and instead fortuitously stumbled upon enormous quantities of opal.

From the Greek ‘opalios’ meaning gem or precious stone, these kaleidoscopic wonders are ever-present in industry literature, in the latest collections of many jewellers, and of course on social media. With plenty of information available for the price, quantity, and quality of precious stones such as diamonds, rubies, and emeralds, at times it is difficult for consumers to gauge the same measures for opals. Of the tons of stones mined, 5% are of a saleable standard, and an even smaller percentage (1.25%) of stones are of high grade.

Frequently asked questions include:

  1. what are opals/what are the various types of opals (if at all)?
  2. how much are opals worth/what is the value of opals?
  3. what are opals used for?

Hydrated silica gel forms in the cracks of stones (the host rock) due to the loss of original water content. The resulting amorphous rock has no crystal structure and measures 5.0-6.0 on Mohs mineral scale. It is also worth mentioning the simulants available, from French manufacturer Gibson – making affordable replicas in the the 70s, later polystyrene latex, and Slocum stone (man-made glass).

The value of these precious gems is dependent on the type, quality and source. One type is common opal (also known as potch) that is the white, opaque type with small spheres displaying blue and violet colours as it oscillates. Precious opal is the other type, that displays incredible fire, with a full range of rainbow colours, and play-of-colour (iridescence) – consequently the latter is deemed to have higher value.

Opal miner Sue White discusses the properties of black opal:

After 100 years they are still mined in Australia (notably NW Lightning Ridge New South Wales for black opal, and Coober Pedy N South Australia). Additionally today opals are found in Brazil, the Czech Republic, Guatemala, Honduras, Italy, Mexico (also mined centuries ago by the Aztecs), Romania, South Africa, the USA and Zimbabwe.

Opals can come in the form of polished boulder opal, or fashioned into cabochons, rings, necklaces, cameos, or enjoyed as loose stones. They were prized possessions of the Ancient Greeks (much like how we value diamonds today), and used by the Romans in jewellery. It is no wonder Pliny the Elder famously praised the “unbelievable mixture of colours”.

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