Opals: How to choose the best gems
AUSTRALIAN OPAL IS NOT ONLY THE WORLD’S MOST FASCINATING AND COLOURFUL GEMSTONE, IT CAN ALSO BE A SOUND LONG-TERM INVESTMENT.
CALLED ‘THE RAINBOW STONE’ by Australia’s Aboriginal people, opal is without doubt one of nature’s most remarkable gifts. It is now recognised as one of the five precious gemstones in the world, along with diamonds, emeralds, rubies and sapphires, and is an excellent investment.
While small amounts of opals may be found in other countries such as Ethiopia, Mexico and the USA, Australia produces more than 90 per cent of the world’s supply. The romance of the opal is in the gem’s incredible ability to expose an infinite number of colours, forever moving with the light. Mined in the outback of Australia across three states, it is as much the call of the outback that lures the opal miner and keeps them going. Scorched landscapes and blazing red sunsets, the night stars from horizon to horizon, this is a hauntingly beautiful country that penetrates one’s soul.
The elusive opal was formed millions of years ago when liquid silica filtered down into the faults and fissures of sedimentary rock. When the water content evaporated, tiny spheres of silica remained and over time were solidified.
The intensity and combination of colour occur with such variety that each gem has an individual character. In 1964 the CSIRO (Australia’s national research laboratories) unlocked the riddle of why opals have such colours.
Opal is composed of minute particles of silica in closely packed spherical aggregates. It is the varying arrangement of these particles (and, of course, cavities) that causes the reflected light to be split into the full range of colours of the spectrum.
There are three main production areas in Australia for mining opals. There’s the bright and beautiful Queensland boulder opal which is mined around the Quilpie area in Western Queensland.
Lightning Ridge in New South Wales is the home of the famous black opal which derives its name from the colour of the nobbies or pieces of rough opal in which the gems are usually found.
The third area is Coober Pedy and Mintabie in South Australia. Coober Pedy is an Aboriginal name, meaning ‘white man in a hole’, which describes exactly what miners still do today—live underground to escape the fierce heat of summer. This is where the white or milk opals are mined.
The value of an opal depends on the amount and brilliance of the colour, preferably being evenly distributed across the face of the polished gem. The greater the spectrum of colours from red to violet, the better, with crimson, reds and orange being rarer than the greens and blues. Milkiness, cloudiness or greyness detracts from the value.
Ideally, the greater the number of colours, the more prized the gem, and if these are arranged in a block pattern, more value is added. The extremes are pin-sized dots of colour (pinfire) to one large sheet of colour (broadflash) covering the whole stone. The elusive ‘harlequin’ is the ultimate in this form but is very rare.
Shapes of the finished opal vary according to the characteristics of each stone. Boulder opal is usually cut in baroque or free form, whereas seam opal is at its best presented in cabochon (domed) form.
If you are buying an unset opal, it is important to consider the way it will eventually be worn. For example, some opals will offer a better play of colour when worn vertically, as in a brooch or pendant, whereas others are best flat, as in a ring setting.
There is a great deal to consider when investing in your opal, but expert advice is available for your complete pleasure and pride in an ever-inspiring piece of jewellery. Above all, buy the opal colour that appeals to you. Enjoy your purchase, knowing it’s geologically millions of years old, but will give you pleasure every day of the year.
Opals—truly nature’s own fireworks!
Black opal pendant enhancer with diamonds, set in 18kt yellow gold. Designed by Fiona Altmann, Altmann + Cherny.
Opal set jewellery from Giulians.
The Great Reef Collection by Opal Minded.