|
 |
|
 |
|
 |
|
|
 |
|
 |
|
 |
|
|
|
|
|
Australian Opal
Every opal has a unique play of colour and pattern. When you select an opal, you have a true original. Enjoy your own special opal and its unique, ever-changing colour and pattern. Read on for information about how opal is formed; how it is mined; different kinds of opal; and how opal is transformed from its rough state into a finished gemstone. Want to know more about opal? Please contact us and we will be happy to help. Opal Gemstones to Purchase
Solid Opal Less Than $200 Opal from Lost Sea Opals Lost Sea Opals specialises in Lightning Ridge black and crystal opal.
Our opals are cut by professional gemcutters who ensure flawless shape and impeccable finish. We supply everything from expensive showpieces and small bright black and crystal gem opals, to commercial grade opal and calibrated doublets. We guarantee the quality of our products.
Click on one of the links above to go directly to opal in our online shop; or read on for more information about opal. What is Opal?
Opal is one of the world's most rare and valuable gemstones, and it comes in every colour of the spectrum. Opal is made of tiny, microscopic spheres of silica. It is these tiny spheres that give opal its amazing colours, by breaking white light up into rays of different colours. When white light enters a precious opal, it hits the spheres of silica. The spheres split light into rays of different wavelengths, which we see as different colours. The colours and patterns in an opal are determined primarily by the size and arrangement of the silica spheres it contains. Where does opal come from, and how does it form?
The basic ingredients for opal are water and silica - but the exact conditions required for opal formation are still not fully understood. On the extremely rare occasion that conditions are just right, silica collects in spaces within the rock and gradually hardens to form opal. The opal takes the shape of the space it is filling. Where the rock cavities once contained plant or animal remains, opalised fossils are formed.
Opal mining is just about the only mining enterprise still run by individual operators or small partnerships, rather than by large companies. This is mainly because opal is so rare, and occurs so unpredictably. Despite its rarity (indeed - because of it!), opal is extremely valuable, and is an important export product for Australia. It is also this chance of 'striking it rich' that inspires opal miners to stick to their tough and risky occupation.
Most opal is mined from underground, where it formed. In Australia, opal is found down to around 25 metres below ground level. Occasionally opal is found on the surface after it has been brought there by years of weathering and erosion. In some areas of Australia opal is mined by the open cut method, whereby all of the ground above the opal is removed to expose the 'opal level ' - the layer of rock in which opal may be found. Material from this layer is known as opal dirt. Where opal is deep underground or is found in only small, elusive patches, the open cut method is uneconomical. Moving such large amounts of earth is too expensive unless there is a good chance of finding a relatively large amount of opal.
At Lightning Ridge, miners tumble or wash their opal dirt to remove bulky clay or sandstone from the opal. This washing process is done in a large agitator - usually a modified cement mixer. The products of the washing process are called tailings, and these are carefully sorted for any trace of the elusive, precious opal. TYPES OF AUSTRALIAN SOLID OPAL
Black opal is opal with gem colour on a natural dark base. The dark base colour shows up the gem colours more brilliantly than in any other kind of opal. When the base colour is dark grey rather than black, the opal may be referred to as 'semi-black' or 'grey'. Black opal is the most rare and valuable opal type. Nearly all of the world's supply of black opal is mined at Lightning Ridge in New South Wales.
Light opal contains gem colours sparkling from a white or pale-coloured body. Light opal is mined mainly at Coober Pedy, Mintabie and Andamooka in South Australia and at White Cliffs in New South Wales; some light opal is found at Lightning Ridge.
Crystal opal contains gem colours in a transparent or semi-transparent body. Crystal opal can be extremely beautiful, and is often used to make opal doublets or inlay jewellery. It is mined mainly at Andamooka in South Australia and at Lightning Ridge in New South Wales.
Common opal is opal that does not contain gem colours. Common opal has the same chemical composition as gem opal; but whereas gem opal contains microscopic spheres arranged in a regular array, in common opal the arrangement of spheres is irregular. The best-known kind of common opal is potch, which may be black, grey, white or amber-coloured. A natural backing or body of black potch is a defining characteristic of black opal (see 'Black opal' above).
An opal doublet is a slice of gem opal fused onto a piece of dark backing material (usually dark potch). The dark backing enhances the brilliance of the opal, giving it an appearance similar to black opal. An opal doublet can allow you to own a beautiful opal gemstone for far less than the cost of an equivalent solid black opal. An opal triplet has three layers. Gem opal (usually a very thin slice) is sandwiched between a piece of dark backing material and a cap of transparent quartz. The transparent cap protects the opal layer and adds depth to the triplet.
A solid opal is more valuable than a doublet of similar colour, pattern, brilliance and size; and an opal doublet is more valuable than an opal triplet of similar appearance. Lost Sea Opals sells quality solid opals and opal doublets, and will happily provide you with the right advice to help you select an opal to suit your budget and taste. From rough opal to opal gemstone
Opal direct from the mining or washing process is called rough opal. An opal cutter will take a piece of rough and first use an abrasive lapidary wheel to carefully rub away the opal's covering of stone or potch, to reveal exactly where the gem colour is. At this stage, the opal is called a rub.
The opal cutter's job is a highly skilled one, involving a constant process of feedback between eye and hand, informed by experience and by sensitivity to this marvellous and unique gemstone. The rewards are the thrill of discovery - each opal gemstone is different to the last, its secrets waiting to be revealed - and the satisfaction of crafting rare and exquisite opals, each one absolutely unique. Every opal contains an infinite number of hidden faces. It is the cutter who determines which face an opal shows to the world.
|
||||||||||
We mine, cut and sell 
Opal forms within spaces in rock. It is found within sedimentary rocks, such as sandstone; and in volcanic rocks that have hardened from molten lava with air bubbles trapped inside.
More than 95 per cent of the world's opal is found in Australia. Most of this opal is found in the Australian outback, around the margins of an ancient inland sea that once covered almost one third of Australia - around 110 million years ago, during the Cretaceous period. The opal is found in small pockets between layers of sandstone in clay beds that once formed the floor of this great lost sea.
Some scientists think this Australian opal took thousands of years to form, at high temperatures and under great pressure; others think the opal formed relatively quickly, at about 20 degrees celcius. It seems that at least some opal formed when bacteria took silica from the surrounding clay or stone, then deposited it in spaces in the rock, where the silica became opal. 
Scientists continue to try to understand the details of how opal forms - and opal miners follow this research with great interest, in the hope that knowing how opal formed will give them a better chance of knowing where to find it.
The equipment used for opal mining depends on whether the opal is mined underground or by the open cut method; and also on the miner's budget. Equipment ranges from hand picks through jackhammers to small machines called diggers and boggers; right up to large earth moving equipment. Most miners start out with the basics, then upgrade when they strike opal. 
In these cases, underground mining methods are used. A narrow vertical shaft is dug or drilled down to the opal level, then horizontal tunnels called 'drives' are dug out in the search for opal. Miners climb up and down their shafts on ladders; opal dirt is usually taken out of the mine using an automatic hoist or a blower, which uses suction to transport opal dirt out of the mine and into a truck waiting above. Most opal mining at Lightning Ridge is done this way.
Boulder opal is gem-coloured opal found within a body of ironstone or iron-laden sandstone. It is named for the boulder-shaped lumps of ironstone in which it is often found. The dark-coloured stone gives some boulder opal a brilliance similar to that seen in black opal - but the gem colour usually occurs in thin, wavy sheets, so boulder opal is often cut with rock matrix showing in the face.
OPAL DOUBLETS AND TRIPLETS
It is an amazing thing to stand in an underground opal mine and see the brilliant, sparkling colours of opal wink and flash from walls of clay and sandstone. But most gem opal comes into the daylight hidden by sandstone and/or a non-precious, black or grey form of opal called potch. These must be removed to reveal the gem in all its glory.
The opal cutter shapes and polishes the opal gemstone using a series of increasingly-fine abrasives and polishes. With each pass over the cutting wheel, the cutter reassesses factors such as the location, depth and direction of the band of gem colour; the presence or removal of impurities; the brilliance of colour, the patterns it forms, and the way these change within the stone. Removing a fraction of a millimetre may reveal the brightest face the stone can have.....but it could also ruin the stone forever. 