Australian opal was discovered by German geologist Johannes Menge in South Australia in 1849. Today, opals are mined in three states along the Great Artesian Basin on the shoreline of what was once the Great Inland Sea. These areas form part of the great Australian outback, known for its harsh, dry climate and inhospitable living conditions. It’s surprising then that such colourful, lively gemstones are recovered from its soil.
Opal is Australia’s national gemstone and it can convey a mood that is as varied as its type – from the delicate milkiness of white Coober Pedy opal in South Australia to super-clear crystal opal from Andamooka (also in South Australia) that is filled with light and ablaze with brilliant colour.
Dramatic streaks of colour are typical of Queensland boulder opal, material that is attached to dark ironstone host rock and is usually fashioned into uniquely-shaped, sometimes undulating forms perfect for custom-made settings.
Matrix opals from Koroit in Queensland offer a vermicular network of brilliant glimmering colour against a dark-brown sandstone or ironstone host. Split pairs of matrix are ideal for earrings and make a dramatic statement as each half mirrors the other.
There are yet more treasures to be found in the Sunshine State. Yowah nuts from Yowah are especially popular with fossickers as they hold a secret that is revealed once split. When cracked open, these concretion-like kernels may expose solid opal, a web of thin veins in a matrix-like effect or perhaps no colour at all.
The most famous opals – blazing fireballs of colour set against black backgrounds – are typical of high-quality Lightning Ridge material from NSW, the home of the Australian black opal. According to Aboriginal legend, a huge wheel of fire fell to earth and sprayed the countryside with brilliant coloured stones.
Some locations are famous for particular types of opal but varieties like opalised fossils are common to all of the major Australian fields. These fascinating relics are reminders of plant and animal life in ancient times.
While found in small amounts in other countries such as Brazil, Indonesia, the Czech Republic, Ethiopia, Mexico and the US, Australian opal is considered the finest and brightest in the world. In fact, designers from all over the world derive inspiration from the rainbow of colours seen in Australian opal, from Queensland-based Margot McKinney to international jewellery houses Piaget, Chaumet and Louis Vuitton.
It is NSW that produces the largest proportion of Australian opal in terms of value yet the value of an opal is determined by many factors including type, colour, brightness, size, shape, weight and pattern. The most prized pattern of all is harlequin, a chequer-board arrangement of broad blocks of colour reminiscent of the colourful costumes worn by medieval court entertainers.
Opal is a softer gemstone (5.5–6.5 on Mohs hardness scale) compared to emerald (7.5–8) and wearers should take care to avoid abrasion and hard knocks.
Each Australian opal is unique and should be appreciated on its own merits. Opal specialists can help you find the perfect piece.