About Me Stuart Bird, I have been cutting and polishing Opals since 1993, I now specialize in all aspects of Opal Cutting & Carving, below is photo of a Multi Slicing Machine, otherwise called here as a Triplet Slicer.

You can see the sliced opal sticking through the blades, (220 of them) normally you would not see it like this, but I stopped the machine and washed it down so I could take the photo, the machine was only a few weeks old when this photo was taken, & that was in 1994, cost of the Slicing Machine now is well over AU$5000.00.

Over 90% of the world's precious opals are mined downunder in Australia and most of that is found in Coober Pedy and it is now recognized as Australia's National Gemstone.

History : Opal, from the Greek, "Opallos" meaning to see a change of color, is a formation of non-crystalline silica gel.   Firstly it is a closely – packed array of millions of spherical partials of Amorphous Silica, stacked in a three dimensional grating.   Because of this special grating, it is the only known gemstone that has the unique ability to diffract white light or sunlight into all the beautiful colors of the rainbow.

Impurities play no part in creating the colors of the opal, as is the case with many other gemstones.  Color is created when light is split by the voids that been formed between the spheres.  The size of the voids is critical to the angle at which the light is split, hence the color produced.

To produce color visible to your eyes, the spheres that form the voids must be smaller than 1500 angstrom for violet, indigo and blue, nor larger than 3500 angstroms for orange and red.

Millions of years ago, between 85 & 120 this gel seeped into crevices and cracks in the sedimentary strata.   Through eons of time and through nature's heating and molding processes, the gel hardened and can today be found in the form of brilliant opals.

The Opal is set apart from other gemstones, because of its characteristic appearance, displaying sparkling prismatic colors which change and flash as you turn the stone in your hand.

No two opals are exactly alike!  It was not until the development of the electron microscope that science could establish the cause of the flashing spectral colors within the Opal.

Australia is the world's most important source of opal and the opal miner is a strange breed of individual, (and that, I am)  he chooses to lead a Spartan life in a particularly barren and dry corner of the world while he searches for his rainbows.  To escape the extreme temperatures during the summer some of us, about 50% burrow a home underground, called Dugout's.

Opals are usually found in sandstone or claystone (called bulldog shale).  Deposits are spread over a wide area, and there is little clue to their location.  Mining is done on a small scale by individuals and not large companies, with hand-operated machinery and small tools, hand picks, electric jack-picks and of course explosives.

Over the past century scientists have become highly skilled at creating laboratory facsimiles of fine gemstones.  Far from being mere look-alikes, these synthetic gems are made of exactly the same material that nature uses and mimic the natural structure almost perfectly.

Synthetic Opal first came on the market in 1974 and has been improving ever since.  A skilled gemologist like a member of the American Gem Society can distinguish it from natural opal by viewing it under magnification, but to the untrained eye it does looks natural.

Because opal displays a whole rainbow of colors, it can be worn with any color outfit.  It is usually cut in a dome shape [cabochon] and set in rings, earrings, pendants, bracelets and pins.  It may be joined by accents of ruby, sapphire or emerald to enhance particular color flashes in the gemstone.  A fine opal piece is often guarded in a web of small diamonds as are other exceptional colored gems.  Some opals are fashioned into beads [but they are rare] for a major contribution to a woman's total look.

Opal is made up of amorphous silica spheres with a little water in the structure.  Precious opal consists of silica spheres of similar size arranged in regular layers.  This structure results in the diffraction of light, the wavelengths of white light being separated into the spectral colors.  Red is the rarest color and can only be produced when large sphere sizes are present.

Opal Value is based on the following criteria: color, number of colors, type of pattern, brilliance, perfection of the stone, the cut, the size and unique color patterns or features, and the rarity of the variety of color and or pattern.

Cut and polished opal is priced according to the value per carat (0.2 grams) so that value comparisons can be made.

There are 5.5cts to the gram and 30.103 grams to the troy ounce.

Is it black opal, semi black opal, crystal opal or light based opal and don't forget if it's got lots of Red in it, as Red is the rarest color, it will cost more.

After you have studied this section below, you will quickly see why some opals are more expensive than others.  If you are still a bit confused, just let us know with an email and Stuart will explain to you what you want to know. (if he can)

Should you choose to make a purchase from us, we have an International Guarantee of quality.

You may return your purchase for refund, no questions asked.   Please take note of freight and insurance details in our returns policy in this regard.   Feel free to email and to ask all the questions you like.

You can also read Valuing and Understanding opals prior to purchasing.

Precious Opal is opal which exhibits the phenomenon known as play of color produced by diffraction of white light due to opal's microstructure.

This is composed of an orderly arrangement of spheres of silica in regular three dimensional grid producing colors by diffraction and interference of light waves traveling through transparent silica spheres and voids.

Black Opal is opal which shows a play of color within a black or dark body color when shown face up.

Black Opals are the rarest and most valuable of all the opal varieties and command the most money. Their beauty is derived from their bright colors on a very dark background.

These are mined at Lightning Ridge and Mintabie.  A solid piece of opal with a natural black or dark background, ie a natural doublet, this makes the stone darker on top.  Black opals come in all color variations and range from pitch black to gray giving the stone are darkish appearance when seen from the top. There are 7 shades of black in Lighting Ridge.

The "black" in black opal means the gemstone has a very dark body tone, a black opal can be crystal or opaque.   The rarest color is Red, next is green, orange with blue as the most common color.

Semi-black opal has an inherent darkness in it's body color when viewed against a white background. Mid-gray stones are termed as semi-black.  About 70% of the black opals come from Lightning Ridge, 30% from the Mintabie opal mines. These are the only two areas in Australia producing black opal, but Coober Pedy also produces some semi-black opals.

Is BLACK OPAL really BLACK? the answer is NO, Black opal has a natural black potch base or dark body color against which the play of color shows up brilliantly.   Black Opal is Found mainly at Lightning Ridge in NSW and some areas in South Australia, this magnificent gemstone is the most valuable form of Opal.

Ablaze with color, its dark appearance distinguishes it from white or light opal.   Black opal is the family of opal which shows a play of color within or on a black body tone when viewed face up and according to the proposed opal nomenclature.

Remember that the black in black opal means the gem has a very dark body tone, where body tone refers to the darkness remaining once you remove the play of color.   The trade generally accepts black as those stones that have a very dark appearance if placed on a white background, view the stone from every angle.

There will be some conjecture amongst the experts as to when a stone a stone falls on the Black and Dark opal border.

Updated on the May the 1st - 2007
We are now finding Black Opal here in Coober Pedy, at the Allen's Rise field some 55 kilometers south of Coober Pedy and then 15 kilometers into the west off the hwy, it is a shallow field so I believe and most miners use Bulldozers or Excavators to get down to the levels, this opal is equal to if not is some cases better than the lighting ridge opal, there have been some stunning finds there so far.

The semi-black opal is found on most fields, it's background color ranges from gray to near black, one of its distinguishing characteristics is an almost smoky appearance.

Semi-black opals are from the same family as black opals, but they are not as dark.

Light Opal is opal which shows a Play of Color within a white, gray or light body color when shown face up.   A solid opal with an opaque light background.

White Opals are usually the cheapest of all the solids, they are opaque in color and are mined mostly at Coober Pedy and a few other opal fields.

The variety is known as white opal and has a light background, and the colors displayed lean toward the pastel hues.

Light opal: range in base color from white to yellow and if a light opal is translucent, it is a semi crystal opal or crystal opal.

Crystal Opal is transparent or translucent opal where the colors are sharp and visible below the surface.   A sold piece of opal without a natural black or dark back, the stone has a lighter, more delicate color on top.  Crystal opals come in all color variations.

Crystal Opals are transparent and display bright vivid colors.   An opal with a brilliant crystal appearance allowing you to look down into the stone.   The light background of this opal is translucent.

Crystal opal has a colorless background and exhibits play of color, but, unlike white or black opal, it lets light pass through it.

This type of opal has a degree of transparency which allows the colors below the surface to be visible.

Some believe the to be the most beautiful.   Crystal opals can be either light or black crystal.

By crystal varieties definition, crystal opal is clear enough to read through against a light surface but it's colors spring to life when viewed on any dark surface, the more transparent the stone is, the more it is worth.

Jelly Opal is transparent opal with a jelly appearance and pale indistinct colors.

Jelly Crystal opal, is a solid crystal opal that is extremely translucent, to the point of being almost totally transparent.

Opal that is colorless, transparent to semi transparent and has little or no play of color is called jelly or watery opal.

Taking Special Care for your Opal:

Never: Apply oil of any kind to any opal, oil will not soak into a solid opal and does it no good!

Oil can have additives that can possibly pit the surface and certainly will make a highly polished stone look dull.

Sudden temperature changes can cause a solid opal to crack or craze.

Water, a solid opal may be kept in a small container of water for extended storage to protect it from sudden temperature changes.

Water will not effect the opal stone, nor will it soak into it, no matter how long you leave it in there, some people think that by putting a opal into water you will put some of the water back in the opal, this is false.

Never soak doublets or triplets in water, water soaking can effect the glue etc, attaching the crystal cap or bottom section.

You can clean the opal stone itself with a soft cloth and Methylated Sprites, not sure what you call it in the States, but it is what a Cutter puts in there Alcohol Lamps for Dopping Stones, just put a little an the cloth and give the opal a soft rub, this will clean the stone and also take any oil that has got onto the stone, remember even your fingers have oil on them.

Opal Jewelry:
A mild soapy luke warm water solution and a very soft brush may be used for jewelry set with solid opals, making sure that you rinse off the piece with clean water after cleaning.

The safest cleaning method is to use a damp cloth followed by jewelers polishing cloth for the metal.

Boulder Opal is mainly mined in Queensland, Australia.

Boulder Opal is where precious opal has formed on or in brown ironstone boulders.   It is a solid piece of opal, sometimes very thin with a natural brown ironstone back, giving it a black or very dark opal appearance from the top.

It is a Mother Natures Natural Doublet, cannot be called a solid opal because it is of two different composites.

Boulder opals come in all color variations and boulder opal occur naturally with ironstone on its back, which forms part of the gem when cut, these are mined in Queensland.

Boulder opal is similar to black opal except that the foreground color is very thin and sits on a brown ironstone base, these stones at times can come with interesting hills and valleys on the surface. (meaning that the surface is often, but not always, undulating)

These stones are preferred by people who are more progressive in their jeweler tastes, often boulder opal has ironstone inclusions in the foreground and all sorts of odd shapes which makes them a designers delight.

Boulder is a variety of precious opal which has an ironstone host rock forming naturally as part of the gem and boulder opal can be black or light depending on the appearance of the stone when viewed from the surface.

Boulder opals include the boulder opal, boulder matrix and Yowah Nut variety.

Boulder opals with good color play are nearly as valuable as black opal.

Matrix Opal is porous opal from Andamooka in South Australia, often dyed dark or carbonized with sugar and acid to simulate Black Opal.

Andamooka Matrix, a more porous opal found in the mining field of Andamooka, when it comes out of the ground it is quite pale but by treating it with a carbon dye process it eventually looks like real black opal.

An Andamooka matrix opal can be an affordable alternative to a genuine black opal but buyers beware an honest opal dealer will tell you whether you are buying an Andamooka matrix or a genuine black, a disreputable dealer may not.

The Yowah Opal Field is situated approximately 1000km's (600 miles) west of Brisbane, in Queensland, Australia.

Yowah is known for it's unique and distinctive matrix opal and much sought after Yowah Nut Opal.

The opal field itself is quite small, about 2.5 square miles, in this extremely harsh and arid section of Queensland, where the only reliable water comes from the Artesian Basin, hundreds of feet underground, the finest gem quality opal are sometimes found here.

Yowah opal's have become world renowned for its beautiful picture stone, Yowah Nut (kernel of crystal) and ironstone matrix opal.

Yowah Nut, brilliantly colored opals nested in a nugget of ironstone.   Though the opal center is sometimes separated from its ironstone nugget, many beautiful and unusual jewelry pieces are made by keeping the nugget and its center-opal together.

Skin to Skin is a term that we use here in Coober Pedy, I don't know about the other opal fields.

It means that a piece of opal or a cut opal stone that is Precious Opal from top to bottom or, to put it another way all the way through.

Seeing that all opal found has a Skin on the outside, it is this skin as we call it, that you can see when you are looking at opal in the rough and if you look at it from the top or bottom you normally cannot see anything but a rough surface.

If the opal in between this top and bottom Skin is solid opal ie: all Precious Opal it is called Skin to Skin Opal, therefore opal or a cut stone that is Skin to Skin will cost more than opal, that say is half opal and half potch.

This is because you are getting more precious opal in the stone which you cannot see in a photo of the stone, that is why I will always mention it in the write up and also take a photo of the back of the cut stone.

Assessment of the observable play-of-color:

Play-of-color within the opal is the most difficult factor to judge for any opal.

Its brightness:   How bright is the overall play-of-color?

Its spectral range:   What range of colors is visible in the play-of-color ?

Its saturation:   How pure and vivid are the colors forming the play-of-color

Its pattern:   What is the size, shape, regularity and rarity of the play-of-color?

Its consistency:   Is the play-of-color, pattern, brightness consistent over the whole face of the opal stone?

Its directionality:   Is the play-of color visible from all directions as the opal is rotated?

Play of color is the way in which colors change as an opal is tilted, moved or rotated in different directions.

Certain opals display different colors when viewed from different directions, or when the stone is turned, or when the light source is moved.

This phenomenon, called the Play of Color, gives a opal stone color flashes, or schillers of different colors which vary from stone to stone.   The play of color in many Opals is truly exceptional and unsurpassed.

This particularly applies to a set opal stone that is worn displaying sparkling prismatic colors which change and flash as you turn and move the stones body around.

Fire Opal is also fairly transparent, but its background color may be yellow, orange, red or brown, sometimes it doesn't even have the typical play of color.

It's often called Mexican opal because Mexico is a major source of this type.

Fire Opal with a red body color is also known as cherry opal.

Opal stones can be cut into a wide range of popular shapes.

Oval is by far the most popular shape, next would be the circular or round shape.

Followed by teardrop, square, rectangle, and triangle are also other common shapes, for me personally I prefer the freeform, then every stone I cut is an individual and a one and only of it's kind.

Opals can also be a freeform from carving the opal, as some opals I find cannot be cut in the normal way, as I would loose too much of the precious opal, so using a carving tool, (I use a Dremel) I grind away all of the sandstone and impurities, then polish the stone, we are then left with is what Mother Nature gave us, a solid Opal Freeform.

A opal doublet is when a solid piece of opal is attached with glue to a piece of background material made to look black as a two piece composite. (no crystal cap to cover the opal)

This sometimes gives the doublet an appearance of black or semi-black opal on top.

The opal and backing are stuck together with a glue to form a doublet, the stone being made of TWO pieces, hence the name Doublet.

The glue I use is impervious to water, acids and solvents, BUT neither triplets or doublets should ever be immerse or soaked in water for any length of time, as it is still possible for the water to penetrate in between the two materials over time depending on what the cutter has used to make the two surface's black and what glue they have used, so play it safe and keep them out of the way of water.

There are different materials used for the backing, black potch (nobbies) from Lighting Ridge is used by some cutters if you can get hold of it, but here in Coober Pedy we use (no crystal cap to cover the opal) Glass, Boulder Ironstone, Black Obsidian or just Plain Old Potch, but the most common used would be black obsidian.

I personally use the black obsidian and boulder ironstone, the reason being is that opal is found on or in boulder ironstone naturally, so it makes for a good mate as opal likes it and obsidian is almost the same composite as opal in hardness and makeup.

Doublets come in all the color variations, if you want to see if it's doublet, look for the glue line and straight edges between the precious opal and the backing, if the stone has been set in jewelry you may have trouble trying to tell the difference between a solid and a doublet.

Opal Triplets are made up of a very paper thin slice of precious opal glued to a black base of glass or potch and covered with a protective clear quartz crystal cap glued on top. (three sections)

These Tops as we call them are normally factory made in Germany or Austria and we buy them by the bag of 100.

Commercial triplets (ie: calibrated) are usually cut by the thousands at one time, when I used to cut a batch (don't cut them anymore) it is normally about 4 thousand that are on the sticks before I finish them off.

In the case of making Freeform triplets I use toughened window glass as the top, then it cut to shape and then polish it.

Triplets come in all the color variations you can imagine.

Boulder Opal Doublets are usually made from a light transparent opal which is normally crystal or semi-crystal attached by gluing it to a ironstone backing with some black added to enhance the opals color and make it look darker.

Although Gray or light opal can be used, in fact any kind of opal can be used and we just use the boulder ironstone as a backing for making any doublets, as I do when making my Inlay/Mosaic stones.

This is how I sometimes make a skin shell into a doublet, using the boulder ironstone to strengthen and enhance the thin opal, that normally could not be cut or set in opal jewelry if left in its natural state.

Common Opal is opal which does not exhibit a play of color.

Common opal is usually made up of silica spheres of non-uniform size with irregular stacking.

Opal that may be dull and valueless, in which case it is called common opal.

Common opal occurs in abundance throughout the world.

One form of common opal found in association with opal of value, is potch and makes up roughly 96% to 97% of all the opal found here in Coober Pedy.

In color, potch may be white, gray, black, amber; it may also be honey-colored, watery clear, or a mixture of all these colors.

Potch is the name that common opal is called here in Coober Pedy.

Potch is also the backing that occurs naturally on solid opal and varies in thickness.

Potch: What is it? Potch is defined as Common non-precious opal without diffracted colors!

About 97 percent of opal from the opal fields here in coober pedy is potch, only 3 percent is of any value.

Of this 3 percent about 95 percent of that is mediocre grade, with only 5 percent of real value.

It is this small percentage that constitutes the magnificent opal which we call precious opal.
(No wonder precious opal commands such a high dollar price)

Potch consists of random sphere sizes in regular layers and is opaque usually white, gray, bluish or black.

Precious opal in many cases often forms as a layer on potch, this is the case with the True Black Opal, which is Red on Black.

Opalized shells, crustations, sea creatures, snails, animal claws and bones, are some of the many objects that over time can become Opalized when buried in the unique environment of Australian clay and left undisturbed.

That is what the general conception is, but in actual fact what happened was that over many thousands of years the buried shell etc, actually disintegrated and turned to dust or a fine powder and left a cavity, much like a jelly mold, as the opal silica jell seeped its way down through the sandstone as it was being formed, it found and fill all the cracks and crevasses it found on the way down.

This is how we have many types of Sea Shells, Pipes and Verticals which are the result of cracks and are most times found in a upside wedge shape or oblong shape and of course, where we find the most opal is in the Seam or on the level as we call it here, which use to be a seabed.

A specimen is or could be chunk of opal or shell that is either left in it natural state or given a polish or varnish to show off one aspect or feature of the stone.

Opal specimens are sought after by Rock Collectors, who generally display them on a desk or shelf.

With a Specimen Pair, both halves actually fit together, but are usually displayed side by side to show off the opal in the center, very rare to get a specimen pair here in Coober Pedy.

A Opal Specimen could be a cut and polished opal stone that has to many inclusions or may have a crack.

Any eye visible inclusion, such as patches or lines of potch, webbing, (snake skin like appearance) the presence of sand spots and or crystals of gypsum near the surface on the opal, or the presence of ironstone (in the face of boulder opal) the presence of crazing (many surface-reaching cracks and fractures) or it may have to much cotton present that can be seen with the naked eye.

In fact there is quite a lot that can make a piece of opal be classed as a Specimen, but that does not mean that the opal is no good, just means that the price is down and the piece is not as valuable. (for us)

Mosaic Opal, the mosaic opal stone is a man-made creation, slivers or pieces of genuine opal are assembled into an irregular tiled pattern with pieces of black potch or black obsidian framing each unique opal piece.

Most of these very thin pieces are left overs from the slices of opal that we make triplets from.

Mosaic opals make stunning stones for all types of jewelry and allow the jeweler to include a wide range of colors within an affordable piece.

Now, there is a natural stone that looks very similar to mosaic opal.

The natural Phenomenon is called the Harlequin Opal, it is the rarest and most expensive opal.

There are some interesting stories associated with opal settings, some people believe that doublets and triplets are always put into fully backed rubbed in or bezel settings to hide the potch or whatever backing is used or the fact that the stone is a doublet or triplet.

Others believe that full backings are used to protect the stone, Neither is true.

A jeweler could just as easily hide a doublet in an open backed setting as the join line between the stone and the potch backing would be covered by the side of the rubbed over setting, making it difficult to see whether the back of the stone was a different stone or simply the less brilliant side of the same stone.

As not all opals are Skin to Skin, some opal as I have already said lays on potch in its natural state, so in fact is a natural doublet anyway and this cannot be detected when set in a piece of jewelry.

But me personally, I feel that if the stone has color (precious opal) on the back, why would a jeweler want to cover up the precious opal, so there could be some Jewelers who would cover up a back of a doublet & try to make people believe they are buying a solid stone, especially when the back is ironstone or black obsidian, like I use.

Rough Opal Parcels are sorted (Classed) into a few grades: Tops, otherwise called 1st's, then we 2nd's, 3rd's and so on, in a parcel of say 34oz's I have had 7 graded bags, to take out and sell.

Each Number 1 bag has a King stone as we call it, which is the best stone in the parcel, some parcels can have several King stones.

Color is the primary criteria for grading, but the buyer's also take into consideration the size of the stones, (why we have many bags) the number of imperfections and faults and whether a stone has the right shape and thickness to be cut into an Calibrated size or one of the other popular shapes.

If the buyer wants to cut Calibrated Stones from the parcel and the stones are to thick then this will bring the price down as he will say that they is to much waste on the opal and he will not want to pay for any waste, but then it not does take much for an Opal Buyer to try and get the price down so they can make more money out of the Opal Miner.

You can buy rough opal in several different size's, from the largest stones to the small chips.

Mine Run:
Direct from the mine, after the opal has been tumbled (cleaned) and classed into grades, the stones have not been cut or ground down or touched in any way, nor has it been picked over, this means that there is more guess work in the cutting.

Purchasing Mine Run Opal can be risky if you are not very experienced.

Off Cuts:
The miner has removed whatever opal he has a market for and sells you what's left, with off cuts, you can usually tell what you are going to be able to cut.

Cracks:
You must still watch for cracks in the opal because once a crack becomes obvious, a stone can lose half its value.

Rubs:
This can often be the best way of buying rough if you are not very experienced.

The miner/cutter cuts and grinds the stone to removed most of the rubbish just to clean up around the stone, mostly on top and sides so the buyer can see what they are purchasing but should not have made it into a Calibrated Shape or Size nor sanded or polished it in any way this is up the buyer/cutter.

What you have left is the stone nearly ready for the doping and polishing process, then you have the satisfaction of cutting your own stones without the high risk of buying mine run rough, although this practice is mainly confined to opal from Lighting Ridge.

Opal is officially sold here in Australia by the troy oz, there are 20 d.w.t pennyweights in a troy oz, 30.103 grams to the troy oz and approximately 30 oz to a kilo.