Precious is made of Hydrated Silica, SiO2nH2O (Silicon Dioxide)
The hardness of an Australian opal is between 5.5 to 6.5 or more.on the Moh scale of hardness ( Diamond being the hardest at 10 ). Australian opal is a sedimentary opal, and for this reason is the most stable of all opals.
Australian opals are also the hardest of all the world opals.
Mexican and Ethyopian ( Wello opals) opals have to be treated to make them more solid and which most sellers of these opals do not tell you).
Good quality Australian opals do not need to be humidified or kept in water to safeguard them. Australian opals, specially boulder opals, do not need any special care, beside normal care given to a gemstone or diamond or an expensive piece of jewellery.
All our Australian opals are natural and not treated and will last a long time.
Precious opal can be transparent (crystal opal) or opaque.
Precious opal is rare ( rarer than diamonds) and not two opals are exactly the same.
The colours displayed by precious opals (iridescence):
The colours of a precious opal are the result of the diffraction of light. This is why the display of colours will change depending upon the light source. New hues or tones can also sometimes appear when moving or rocking an opal. To photograph opal is a very difficult and a technical process and all the opal colours are not always captured by our digital camera. Also note that the resolution of your display will also affect how clear or bright our opals will appear on your monitor.
Boulder opal: Variety of Australian precious opal having formed in cracks or cavities in brown ironstone or dark grey sandstone, found exclusively in Queensland, Australia.
Australian boulder opal is a rare precious opal found exclusively in Queensland, Australia.
Despite claims made by some opal merchants, any so-called boulder opal found in any other country than Australia, is not a true boulder opal.
Just like any sparkling wine made outside of the controlled region of Champagne in France, cannot be called Champagne.
Being a sedimentary opal, Australian boulder opal is the most stable of all opals.
It will stand different ambiant temperatures without being affected.( unlike some other opals who need to be kept in a humid environment, or even in water, to stop them from cracking or crazing).
It is also the hardest of all opals and does not crack under normal circumstances.
There is no need to keep it in water or keep it moist like most volcanic opals (Mexican and Ethy0pian opals) which have been treated to stabilise them.
Australian boulder opal is found in cracks or cavities of various thickness, in a ferruginous (containing iron) rock, called ironstone.
Australian boulder opal is cut with leaving a thin layer of the mother rock on the back of the opal seam.
It is a very versatile opal as large boulder opals with little opal in it, are carved into very artistic pieces.
When cut and polished, by world standards, Australian boulder opal is a "Natural opal,Type 2".
Boulder opal split: When the opal vein in a boulder is thick, a groove of about one millimeter deep is done around the stone into the opal seam with a diamond saw blade.The stone is then split open.
It results in 2 stones instead of one, almost identical, fitting together.
Depending on the size of the original stone, a pair of earrings, or a full set of earrings, pendant and a ring can be obtained with matching opal colours
Boulder opal matrix: An Australian boulder opal matrix is precious opal mixed with the parent rock rather than in seams or patches.
The parent rock is an ferruginous rock ( containing iron ), and is called ironstone.
It is found exclusively in Queensland and does not need to be treated before cutting or polishing.
The word boulder is used in its name, because it is always found in proximity or among deposits of boulder opal, and the mother rock is the same as boulder opal.
It is not to be confused with Andamoonka matrix from South Australia, of which the mother rock is of a different composition and must be treated before cutting and polishing to accentuate the opal colours.
Our Queensland boulder opal matrix is natural.
It is not treated and does not need to be treated like Andamooka matrix.
When cut and polished, by world standards, Australian boulder opal matrix is a "Natural opal,Type 3.
Black opal: Opal with a dark or black body.
Is the rarest and most expensive opal. Only found in Australia.
Coober Pedy opal:
Coober Pedy is a township with a vast opal field in South Australia.
Coober Pedy produces over 90% of all precious opal mined in the world (mostly white opal but also beautiful light and crystal opal).
It is the main source of opal used to make Australian opal doublets and opal triplets.
When cut and polished, a solid Coober Pedy opal is by world standards, a "Natural opal, Type 1".
Lightning Ridge opal:
A Lightning Ridge opal is a precious opal that has been mined in or around Lightning Ridge, an opal mining field in New South Wales, Australia.
It is renowned around the world for its black opal in particular, but it also produces beautiful light and crystal opal which is used as inlay in opal jewellery. When cut and polished, by world standards, it is a "Natural opal, Type 1".
Australian Fairy opal
Fairy opal is the term given by opal miners in Queensland, to opalised sandstone after treatment.
Opalised sandstone is sandstone ( mother rock of opal ) impregnated with small grains of precious opal.
Opalised sandstone is rather localised and when found, no opal of significant size is present close by.
It appears that the opal formation has been limited and restricted to the sandstone.
It is not particularly common, and opal colours can vary from blue to all the colours of the rainbow ( the latter being rather rare)
It is treated to enhance the contrast between the colour of the mother rock and the colours of the grains of opal.
Fairy opal is considered to be a treated opal matrix. It is, in some ways, similar to treated Andamooka matrix from South Australia.
Crystal opal: Transparent or translucent opal.
Gem quality: Finest grade of opal.
Grey opal: Opal with a grey body.
Light opal: Opal with a light body and light colours.
Natural opal: Opal which has not been treated in any way other than having been sawn, preformed or cut and polished.
Opal doublet: A layer of light opal (usually from Coober Pedy, a vast opal field in Australia) attached traditionnally to a background made of black potch ( black opal without fire), but nowadays to a slice of boulder ( ferruginous stone, mother rock of boulder opal) and passed on by unscoupulous dealers as genuine boulder opal.
It is a composite opal.
It is sensitive to water.
It must not get wet or be immersed in water.
Opal inlay: Crystal opal, with the back blackened to enhance its colours, set into channels.
Opal triplet: Thin slice of opal (usually from Coober Pedy, a vast opal field in Australia) sandwiched between a supporting base and a supporting dome.
It is a composite opal.
It is sensitive to water. Do not get it wet or immerse in water.
Pipe opal: Australian pipe opal is precious opal having formed in roundish or tubular holes in the mother rock, usually sandstone, but can be also found in boulder.
Potch: Opal without any fire.
Rolling flash: Opal displaying colours that roll across the stone.
Semi-black opal: Opal with a dark background but not dark enough to be called black.
Solid opal: Natural Opal that has not been backed or capped in any way.