Aus­tralian opals shine bright

Aus­tralian opal is not only the world’s most fas­ci­nat­ing and colour­ful gem­stone, it can also be a sound longterm in­vest­ment.

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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!

The in­ten­sity and com­bi­na­tion of colour oc­cur with such va­ri­ety that each gem has an in­di­vid­ual char­ac­ter.

THE RAIN­BOW STONE: (Op­po­site page): Boul­der opal and let­ter pen­dants from Gi­u­lians. (Above): Black opal pen­dant en­hancer with di­a­monds, set in 18kt yel­low gold. De­signed by Fiona Alt­mann, Alt­mann + Ch­erny. (Left): The Great Reef Col­lec­tion by Opal...

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