Strictly from the sense of its physical formation, all opal is formed in cavities of opportunity. Sometimes the cavities are large as in ‘slides’ or ‘levels’ which produce thick solid slabs; sometimes isolated as in a clam shell; and sometimes intruding into fine fissures in hard native stone such as ironstone.

But when opal filters into ancient layers of limestone, something truly miraculous occurs.

Limestone is formed over millions of years by the death of countless microscopic plants and animals in waters and bays. The Cliffs of Dover are a well known example. The skeletons or fossils of these early life forms persist, and create myriads opportunities for the intrusion of opal, if the conditions are right.

The microscopic cavities in limestone prevent the opal from forming what we recognize as solid opal with thick layers of fire. However, the opal does form the microscopic equivalent, within these tiny cavities. With the aid of a microscope, one can see a reticulated effect, varying somewhat between the eye of a dragonfly and the skin of a snake.

Limestone appears to us usually as a very white chalk-like stone. This is detrimental to the fire of any opal which has intruded the matrix. There is too much diffraction of the light for any specific color to assert itself to our eyes. Therefore, in the natural state, limestone containing opal appears to have color, but it is washed out and faint. For this reason, it was not viewed as marketable when first discovered.

But when the matrix is wetted, that unmistakable opal fire is there, and no doubt much time went into thinking about just how this material might be treated.

One place in the world where limestone matrix opal occurs, is in a small area of South Australia called Andamooka. For this reason, this material is called Andamooka matrix opal. When it is treated, it is known as Andamooka treated matrix opal. And many of the world’s experts will attest that although the Lightning Ridge black may be the most satisfyingly perfect, the treated matrix is the most brilliant.

They simply make your heart leap !

Who did it ?

It is not known when man first discovered that stones could be treated by fire or chemicals to enhance their qualities, but there are many precious gems today which would never see a market were it not for some sort of treatment.

We also don’t know exactly when it was that someone discovered that limestone matrix opal could be treated so as to improve the richness and brilliance of the opal in the limestone. But it wasn’t considered valuable at first, and little was seen on the market until about 30 years ago.

There’s a story about some of the first blokes who learned how to treat the matrix, and finding the temptation too great, they took some stones to another country, and sold them as genuine Lightning Ridge black opal. After the fraud was discovered, there ensued a time when nobody would buy treated matrix.

But the fabulous colors and rich black matrix of the finest stones really does offer the qualities that make the Lightning Ridge black opal so popular.

How does it do that ?

Treatment of the limestone matrix involves a fairly simple process of simmering the stones in a very rich solution of sugar in water, followed by a period of simmering in a bath of very concentrated sulfuric acid.

The action is that the sugar penetrates into the limestone matrix and then the acid ‘cooks’ it turning the white sugar behind and around the ‘pockets’ of opal, into a black carbon.

The result is that the blackened matrix surrounding the pockets of opal, does not diffract light, and the colors of the opal beam through. The quality of the finished stone is gauged by the brilliance of the fire and the richness and range of the colors.

Treating the Matrix:

First you gotta start with the sulfuric acid. A source can be found easily in the phone book under the ‘chemicals’ section. It must be at least 95%. You cannot use battery acid.

If you are only planning to do a small number of stones, you can buy a quart or gallon, but it is much cheaper by the 25 Gallon drum (about $35).

The smaller containers are much easier to control, and the large drum requires some method of getting small amounts out without spilling.

Next, you need some glassware. There are some plastics that will resist the acid, but it’s much better just to use good Pyrex glass. I found some very nice ‘beakers’ and ‘flasks’ at a local surplus store, but even in the catalogs they aren’t very expensive.

You can use good quality glass containers for storage, as long as they have glass or rubber tops. But don’t use anything but Pyrex (heat-resistant) glass for the cooking container.

You’ll also need some glass ‘stirring rods’. Smooth, solid, and not too long for the height of the beakers.

Last, you need a good controllable ‘hot plate’.

Others talk about using ‘crock pots’ which have a temperature control, but I prefer to have much finer control, and the ability to see into the glass beaker and check the stones while they are cooking. Yes, you can ‘overcook’ them !

I use a commercial hot plate, combined with a very good thermometer. It has a ‘mid-range’ of about 170 degrees F, where it is the most accurate.

Here’s some pictures of the equipment and a batch that has just finished cooking:

Making ‘eye-candy’

First, you must cut and shape the stones but only polish them to a 8000 grit surface or so. You will finish the polish after the stones are cooked.

You must also make sure that the stones are absolutely dry. I choose to put the stones in a jar of methyl alcohol for at least one day before I cook. Longer is ok. Just make sure that when you take the stones out of the alcohol, don’t touch them with your fingers ! The oil in your fingers will diminish the cooking process and even make smudgy differences in the final black background.

Next, mix up the sugar and water. The sugar should be ‘refined’ pure sugar, not brown, not ‘raw’. I fill the beaker about half way, and then stir in the sugar. I find that about 8 ounces of water will absorb about the same amount of sugar.

The water should be distilled, not tap water. It is important because some water systems contain chemicals that will later react with the sulfuric acid, and diminish its effect.

I prefer to heat the water to the working temperature and then add the sugar. I can better watch the thickness of the solution as it develops into a clear syrup.

You don’t want something as thick as Karo syrup, but just a little thinner. As the sugar cooks, it will lose water to evaporation (if no top), and after 24 hours of cooking, it’s likely that you’ll have to dig the stones out of the mess.

When the sugar is dissolved, and the temperature is at 170 degF, it’s time to put the stones in.

Again, don’t touch them. I take them out of the alcohol and let them ‘air dry’ for only a few minutes, (or use a very clean cloth). Then, one at a time, I slide them in, down the side of the beaker.

The amount of time that is required for the sugar step will vary according to the softness of the limestone matrix of the particular stones. But it does not hurt at this time to cook them much longer than might be required.

I’ve seen times when only 15 minutes in the sugar is enough, but sometimes it takes as much as 48 hours. (Some folks say that they’ve had to do this for months !)

The only caveat is that you must make sure that the sugar doesn’t turn to molassas and then to hard rock candy… You can add water to the sugar if you get to it early enough. Too late, and you can’t even stir it.

And stir it you must ! Even if you have a few stones in the sugar, you must stir them frequently to allow the sugar to get to every pore in the surfaces.

Most of the time you can see that the stones have turned a golden color, but don’t expect it. Not even all stones from the original ‘mother’ will turn the same color. It depends on how uniform the original matrix was.

When you decide that they are ready, you can take the beaker off of the hot plate and let it cool. You must be careful at this point that the sugar doesn’t solidify. If I suspect that it’s too thick and may do this, I first pour off most of the syrup to the point where it just covers the stones. Later I can spoon out the stones…

When they are completely cooled, I simply wipe them off with a clean cloth and put them into a covered box until I am ready for the ‘acid’. Again, it’s tempting to handle the stones with your fingers. Admire them, but always use plastic tongs.

The ‘acid test’

Even if you have handled strong acid before, it’s very likely that you will get burned at some point in the process. Hopefully, you will only get a little drop and it will give you good evidence that you must be more careful…

Carefully fill a very clean and DRY beaker about half full with the acid.

Put the hot plate in a place where it is not in some normal ‘path’, and cannot be accidently bumped. I have lots of these places, but I choose always to put a rubber mat of some sort under the hot plate just in case.

Turn on the hot plate, and put the beaker of acid on. (not onto a hot plate)

Let the acid warm up to over 120 degF, and then, with plastic tongs, carefully drop the stones into the beaker. I have a little glass ‘spoon’, that I can use to place them on the bottom, but I never had a problem with a stone cracking by just dropping it in carefully.

After the stones are in, you will see that the acid starts to turn a light brown from the reaction to the sugar on the surface of the stones. If you have not wiped them off well, this may cause complete darkening of the acid right away. This isn’t a big thing, but it will diminish your ability to see the stones in the beaker.

Carefully raise the temperature until it is at (my preference) 170 degF. If you have a hot plate like mine, you must be careful because it will very quickly get to over 200 degF, and it is possible that the stones can crack from the expansion of the water in the matrix.

For the first hour of this process, you MUST stir the stones frequently but gently, and watch how quickly they take on their black color. You won’t want to do anything else at this point… it’s a fantastic experience !

How long !

With some matrix material, you may find that 5 minutes is ok, but 6 minutes is too much ! I’ve only found a few parcels that are this quick, but most require an hour to 24 hours.

The rate at which they change will be constant, so you can get an idea of how long it will take by watching very closely for the first hour. But in any case, you must frequently check them so that you can take them out before they become ‘over done’.

And ‘over done’ they can certainly get ! Muddy, dark, and all but worthless. The only thing you can do at that point is to sand them down and cook them again. Yuk !

As an aside, I use my home automation system to control the hot plate and to warn me of when it is time to stir the batch. In case I go to sleep, it automatically turns off the hot plate and I may have to start the cook again. But generally, I’m all a-twitter when I’m doing ‘Barbeque’…

Fully Cooked

Here’s where it takes a bit of experience to understand just when the stones have achieved the darkest tone that they ever will. Some stones will get black in minutes, others will never do more than get a little darker. Usually however dark they get, the opal in the matrix will be brighter, and that’s the whole point.

Some stones achieve a deep rich black, while others might turn different shades of brown. I’ve seen one parcel that turned a beautiful and sophisticated ‘grey’.

What I have learned to do is to ‘cook’ some sample pieces of a parcel before I cook any finished stones. I keep records, and remember next time I cook something from the same parcel.

Often I cook stones from different parcels at the same time, and must remember that some of them must be taken out earlier than others.

But in some cases, the opal concentration is too high, and the matrix will not accept either the sugar or the acid. The stones get a dark ‘honey’ color perhaps, but will never ‘cook’ beyond that point.

Taking them out of the acid

Whenever you take them out, you must do so very gently, and using the glass rod or tongs. If all are to be taken out at once, then I choose to pour off the acid into another beaker first.

Then I let them cool for 15 minutes or so before I dump them into another bath of cool but more diluted sugar-water. Leave them in this solution for an hour or so, and then take them out, and wipe them off with a clean cloth. Discard the cloth, it will soon disintegrate from the acid.

A little polish and they’re finished

The stones still need to be given a final polish. But here you can really screw up the stones. If you find that you did not surface them well before, you will be tempted to do so now.

But if you grind too much, you will begin to see a lighten-ing of the background color. When this happens, it most often means another trip thru the process.

If you did a good job before the cook, then the surface will only need a quick polish, and it’s finished.

You will find that it is almost always impossible to put the same kind of polish on a matrix opal that you can put on solid opal. I’ve seen some that are almost perfect, but most of the time you will not be able to get rid of the ‘granular’ surface effects.

Well….Almost

Within a few hours and over a period of days, you may see the stones ‘weep’.

This is normal, but some parcels weep more than others. You must keep the stones where you can watch them and periodically wipe them off. The liquid that is weeping contains a lot of acid, and will eat just about any material. After a while, this will stop. If it does not, you may put them back into a light sugar solution and let the acid weep out into that. When you can no longer see any dark wisps of color coming from the surfaces, take them out..

This weeping may slow greatly, but may still continue for several weeks or months. I prefer to keep the stones until I am sure that it has stopped. I have tried other methods of stopping the reaction, but all have resulted in some kind of ‘haze’ or ‘dust’ on the surface, which, being microscopic, is impossible to remove completely, and is always disappointing.

A little more detail:

Although most of the matrix found at Andamooka is broken into small boulders and pebbles, it is sometimes found in large slabs. When these slabs are broken, it is found that the opal is indeed rare and spotty. Therefore, not all limestone from Andamooka yields precious matrix opal.

When opal occurs in matrix, it is found in different grades; varying with the concentration of opal, the granularity of the matrix, and natural inclusions.

Concrete ?

Where the granularity of the matrix is coarse, the stone will not take a polish, and even with a large concentration of opal, it is forever dull unless it is wetted or kept in water. This type is called ‘concrete’, and mimics a type of matrix opal found in Honduras.

When the granularity of the matrix is very fine, there is very little limestone to affect, and the opal cannot be enhanced. This does not mean however that stones of this type cannot be very beautiful of their own without treatment, and even with it.

When the concentration of opal in the matrix is low, of course, there is little reason to mine it. However, larger boulders must be still broken in order to discover small patches. This process greatly adds to the cost of mining matrix opal.

The concentration of opal in the matrix may get so high that treatment is useless and the material is technically solid opal. Stones cut from this material show rich swirling colors but do not have depth, and are slightly translucent.

Another factor affecting the treatment process, is the concentration of dolomite in the matrix. Dolomite is simply limestone which is more dissolved and therefore lacks the permeability necessary for the treatment process to succeed.

Only when the granularity of the matrix and the concentration of opal is balanced just right, will the matrix accept the treatment process.

Inclusions are another element which must be considered when cutting and treating Andamooka matrix opal. As a sedimentary rock, limestone contains various inclusions of softer and harder pebbles, fossilized plant and animal remnants, and sometimes, pockets of solid opal.

Depending on the hardness of the inclusion, it may darken differently from the surrounding matrix when treated. Some inclusions are too hard, and remain light colored or appear ‘dirty’. Softer inclusions may darken beyond that of the matrix.

Often the cutter can take advantage of these inclusions and create ‘picture stones’ which although often obscure, sometimes are startlingly depictive. More often however, these inclusions reduce the appeal and value of the cut stones.

Another problem for the cutter is that of orientation or ‘facing’ the stone. Andamooka matrix is treacherous in that the opal follows natural flows and changes in the composition of the limestone and because the stone is opaque, it is more difficult to predict the direction that the fire will take when shaped and then treated.

The most precious and rare of the Andamooka matrix opal occurs as a careful balance of a soft dolomitic limestone with a medium concentration of opal which has formed in vertically hanging sheets within the matrix. Generally these can be identified readily, even on the field, where larger flakes of fire can be seen in one orientation or another.

Regarding the value of Andamooka matrix opal:

First and foremost is the intrinsic beauty of the final gems. Andamooka matrix exhibits the exact same deep rich colors against a deep black background as does its far more expensive Lightning Ridge cousin.

Next, and probably most importantly, the rarity of the material. Andamooka is a small township north and west of Adalaide along the Stuart highway in South Australia. The precious stones field established around the town is only 5 Kilometers by 13 Kilometers, and being a very small town, (about 300 people), the hardships of life there are very trying.

There are very few opal miners at Andamooka, and even few look specifically for matrix opal. Andamooka primarily is known for a very fine solid crystal opal which exceeds the beauty of that of the Coober Pedy fields to the northwest. This material sells for ten times more than does matrix.

When one considers the amount of opal in the limestone, it is frequently greater by mass in ratio to the matrix, than in boulder opal or other matrix opals.

The fact that it must be treated seems to be the one factor that is limiting the current market perception of Andamooka matrix opal.

The treatment of gems has been practiced since prehistoric times, usually to make them appear to be some more valuable stone. Indeed, when Andamooka matrix is treated, the result emulates the best Lightning Ridge solid black opal. The difference however is that we are simply providing a background for the opal that is already in the stone. The process does not alter the opal, or add opal, or any other brightening or clarifying agent.

It is the opinion of many opal dealers that Andamooka matrix should enjoy a market price which is equivalent to that of other matrix or boulder opal, in that it should be somewhere between 10 and 20 percent of that of solid black opal.

Regarding the health and stability of Andamooka matrix opal:

The treatment penetrates only about one to two millimeters (maybe less) into the material. Therefore, if the stone is gouged deeply, the white base material will be visible. Within reason, the stone can be re-cut, polished, and treated with good success. Should the stone ever be cracked, it can be repaired with greater success than solid opal due to the fact that it is opaque.

The treatment is permanent and care is identical to that of solid opal with one exception. Solid opal will not be affected by detergents or bleach, but exposure to these chemicals without rinsing may cause a light ‘haze’ to develop on the surface of these stones. If this occurs, it can be corrected by re-polishing, or more simply, by a touch of a light body oil.

As with solid opal, various qualities of this material exist. And similarly, the highest qualities are the rarest, possessing brilliance and richness of colors which are the equal to all but the finest ‘solid’ black opals.

Last words

Buy finished stones or plan to cut and treat the rough yourself. Don’t buy rough and then have someone else treat it. This may be the only choice you have, but you will be missing out on one of the most interesting, surprising, and satisfying experiences in your life !

The following story was written by the man in the picture above, our long time friend Uncle George Bucholz.
See another story by Uncle George

At the end of this epistle I will tell you how to get rid of your used acid.

Before I tell you how to successfully treat Matrix Opal, I want to stress to you to get the best material you can afford. You want quality not quantity. I stress this. Any rough opal costs a lot of money, your seller knows this as well as you do. He is not going to make a mistake and slip in a high priced piece of opal. He also can’t afford the mistake. If you want to be satisfied with what you get in the final result after all the preparation and the treatment, then you must get the best matrix opal you can afford. A few beautiful stones are much more salable and make better jewelry than a handful of poor quality. You want QUALITY not quantity.

Now the supplies you will need.

[ 1] —- 1 small ceramic crock pot..
My crock pot does not even have a heat gauge on it for various heats.
I adjust the heat by moving the lid a little crack wider or narrower
any way to keep under 190 degrees Easy to do.

I drilled a small hole in one side of the lid, , close
to the rim, just big enough for the meat thermometer to stick
down into the pot so I can check the heat to keep it about 180
degrees, while i am cooking the stones.

[ 2] —1 Meat thermometer
The small round head with the metal stick body that comes in a long
plastic sheath.

[ 3] —-1 copper tongs about 12 inches long,
or if you can get stainless steel tongs about the same Just great.
I have the copper ones.

[ 4] — 1 small ceramic electric potpourri pot

[ 5] — 1 Large mouth Mason jar — quart size.
This is the old fashioned kind. The one who’s seal is a rubber ring and
closes with a galvanized wire snap at the side. This is
important because this is the jar that is going to hold the used
Acid after your job is done.

[ 6] —- 1 stainless steel strainer
Must fit and cover all the opening of the Mason jar if possible.

[ 7] —- 1 plastic container of Battery Acid
Your nearest battery store that specializes in Batteries will probably
give you a plastic container of battery acid. Ask him.
If not then buy a small container of the acid. Not expensive

[ 8] — 1 box of Baking soda
I do a lot of treating so I get a big box of baking soda from Costco or Sams

[ 9] — 1 box of latex gloves A MUST HAVE

[10] —- 1 Large ceramic pie plate with raised edges to
hold the potpourri pot. I was lucky, I bought a ceramic pizza
pie plate from a 2nd hand store for 1 dollar.

[11] —- 5 lbs of granulated sugar.
I use the Hawaii stuff , never tried the beet sugar.

[12] Safety glasses

[13] fairly large ceramic cereal bowl.

When I started I didn’t know you were not supposed to use battery acid, but I couldn’t get pure sulphuric acid, so I bought battery acid and never looked back. Much easier to use, and not nearly so dangerous.

The first thing I do when I get a new supply of rough rock. I treat it for 3 or 4 days to color it so I can really see what I have and where I should make my first cut.

I have found trying to look at an untreated rock in most instances will not show you the true colors for you to make your judgement.. I try to start the following on a Saturday or a Sunday and then I can do the acid treatment at my leisure.

Fill your ceramic crock pot about 1/2 full of water, add 2 big cups of sugar. It has to be a quite heavy syrupy mixture Plug in and Heat until dissolved. Then add your stones. Now put your thermometer down the hole in the lid, just crack the lid a bit and and watch the temperature rise till 180 degrees.

That is the temperature you are striving for. Stir the stones to thoroughly dissolve the sugar. I control the temperature with the lid. I keep adjusting the lid every hour or so until this temperature is steady.

Don’t worry if the temperature does go over 180 degrees Just so long as the temperature doesn’t go over 190 You don’t want the water in the rock to boil, and it can, if the temperature gets too high.

Keep watching this for the next 3 or 4 days, put water in to the same height, as it evaporates. I do this watching and adding every morning and evening, Stir the mixture at least 2 or 3 times a day. You are making stone soup. However don’t ever try to eat any of it. You can’t cook it soft enough.

On the 3rd or 4th day, I drain all the syrup out of the pot and take the pot and the stones into my shop where I have my potpourri pot sitting on my pizza pie plate. DO NOT HANDLE THE STONES WHILE DRAINING THEM If you do, you can leave your fingerprints on the stone and it can show up on the final product.

I pour the stones into the potpourri pot, scraping out the ones that stick to the crock pot. Then I put on my latex gloves and my safety glasses.

WITH MUCH CARE :

Then pour the battery acid into the potpourri pot until the acid is about an inch above the stones.

I TAKE GREAT CARE IN NOT PUTTING MY HEAD ABOVE THE POTPOURRI POT WHILE DOING THIS SO I do not breathe in any of the acid fumes.

I then stir the stones with a wooden stick or my copper tongs, to loosen up the stones that are sticking together from the sugar. I plug in the potpourri pots. The potpourri pots have built in thermostats so they will get up to about 160 degrees which is just fine with me, I make sure there are no ways a light or a spark can ignite any fumes.

Now get out your cereal bowl and put a couple of tablespoons full of baking powder into it. Fill it about half full of water and stir till dissolved. Put to one side.

I then go about my ordinary chores for about 3 hours and then I stir the stones again and add more acid if needed.

PUT ON YOUR SAFETY GLASSES AND YOUR LATEX GLOVES EVERY TIME YOU DO ANYTHING WITH THIS OPERATION. AND DO NOT BREATHE OVER THE POTPOURRI POTS AND DO NOT LIGHT A FLAME ANYWHERE NEAR THIS OPERATION.

THE ACID WILL TURN BLACK DO NOT BE ALARMED
THIS IS THE ACID EATING THE SUGAR.

At this time it will look like nothing is really happening to the stones, but it is happening, I can assure you. Be Relaxed !! This is a very relaxed operation. No Worries Mate

After about 6 or 7 hours I will look at my stones and I will see some of the most beautiful colors you can imagine. I usually take the stones out of the acid at this time but I will at times leave them in the acid for another hour or two. There is just no hurry. The acid will not touch the opal at all . It will only deepen the black in the matrix. I have by accident left stones in acid for over a year and no damage.

You will also see that the acid has thickened and covers some of the opal so it may be hard to see the colors. Again no worries Mate. The thickness is from the sugar that the acid has been eating. It has not been dissolving the stones.

All, this has been done with latex gloves and safety glasses on !!! I pull the plug on the potpourri pot .

I put my Mason jar in my ceramic plate. I put the strainer on top to cover the opening.and having my latex gloves and safety glasses on, I carefully lift up my potpourri pot and pour the acid into the strainer to expose the opals. If I spill any acid it will be caught in the plate so there is no danger of hurting something I shouldn’t hurt. I dump my opals into the strainer.

Some of the opals may be caught on the sides of the potpourri pot If so, I can take them out with my latex gloves or I use a wooden stick. I prefer the stick to the gloves. I do not want to splash myself at all.

Now all is simple !! I will put my opals slowly a few at a time, into the baking soda water bowl. It will foam and fuss This will neutralize the acid. I Leave them there for about 10 minutes, then I can pick them up and look at them.

Now no fires, no cigarettes no sparks. To neutralize the acid I put a small spoonful of baking soda into the acid in the mason jar Do not close the lid Let it boil. I continue to do this until there is no more boiling. I put at least 2 more spoonfuls in and let it set for a few days, then I put another spoonful in and let it set some more days. I consider it as being dead and I can then flush it down the toilet. I flush the toilet a couple of times more to clear it from the pipes.

Some rocks are very hard and will require several treatments to finally color them. For my successive treatments I go from Saturday to Saturday and do the above. Gradually there will be a great change in color and you can be rewarded with the most beautiful opals you will ever see. Takes a lot of patience for the reward. I have treated some stones for better than 2 months this way, week by week, before I get the color I want.

A WORD :

I want to stress the fact that there is a LOT of work and MUCH patience, connected to getting a beautiful stone.

There is a buildup of brown haze over the stone and it keeps getting deeper and deeper every time the stone is cooked. However, it is a surface haze that obscures the colour flash in the stone.

I take it off each stone by carefully polishing the stone with 18000 diamond grit sanding belt, under water spray. A person can use whatever the person has just so long as the haze comes off. And just so long as the stone is not scratched.

I think I have it all here. Good luck BE CAREFUL
George Bucholz

Perhaps the most inexpensive way to enjoy the beauty of the opal is to buy what are known as ‘triplets’.

A triplet is simply a very thin slice of natural opal, sandwiched between a clear glass or quartz cap, and a plastic or stone backing. The clear cap magnifies and protects the opal slice, and the backing enhances the color of the opal.

The whole idea is that even low quality opal can be made to look like high quality ‘black opal’, and can produce many inexpensive, but very marketable ‘stones’.

 What do they look like ?

This is a very fine ‘super gem’ triplet It doesn’t look like much in this picture
	This is what it looks like from the top Click Here for a much better picture of this beauty.

 How it’s done

Although you could make triplets out of low-grade opal, all you would get is low-grade triplets. Better grade and ‘gem’ grade triplets are made by starting with very fine or gem grade rough opal stone.

Note that this is a very risky business. The cutting process could reduce a very expensive specimen to worthless fragments. Imagine what this can mean if you start with a 3 ounce stone that costs $3000 per ounce !

The rough stone is held against a field of parallel diamond grit saw blades and pushed into the blades by the ‘hold down arm’:

It’s a big ugly machine that produces the intricately thin slices. You can’t see the blades, but they are carried in a changeable block that allows one to choose the spacing between the blades. The thickness can vary between 70 and 120 slices per inch ! To see these blades up close, Click Here

 Not for the Timid !

If you only want to make one triplet out of a fragment of a favorite stone, it doesn’t take much courage. However, if you want to go into the business of making triplets, you’d better have a strong will.

It takes between 3 and 15 hours for the saws to cut thru, and during this time, you must mind the machine to make sure that it has not bound up. Not only can you lose the opal stone, but you can destroy the very expensive saw blades !

Further, if you’re in the business to produce triplets, you need to be prepared to produce thousands every month. For this you need to have more than one of the triplet saw machines.

Not only do you have to have several of the machines, but you also have to have several different blocks of saw blades with different spacings.

 Selecting and preparing the rough

Because they are going to be sliced, the rough stones must be fairly large. Smaller stones cannot be held easily against the blades. Fortunately, white-based opal occurs commonly in larger stones, but remember that this process doesn’t produce the fire. The color, pattern, and fire must already be there !

Here is a parcel of stones which have been selected to be turned into triplets. To see a better picture of the fire Click Here

 Fabricating the triplets

After cutting, the slices must be sorted and graded, and either broken or sawed into sizes and shapes appropriate to their pattern and perhaps ‘to order’.

You must also cut just as many slices of quartz ‘caps’, and as many black stone backing pieces.

Then, the three pieces of the triplet must be glued together with a very fine jewelers cement, and left to cure. It is not necessary to polish the opal slices because the glue will fill the slight imperfections and provide the perfect refraction index.

Next, each of the rough triplets must be ground and polished. Some will become ‘freeform’ shapes, and others will be ground to ‘calibrated’ shapes and sizes.

 The final product

It may seem like blasphemy to reduce a splendid opal specimen to minute slices, but, properly done, the result produces a large number of triplets which can be sold at a very nominal price. If you are skillful (and lucky), the quantity and the effort will more than make up for the differential in price.

Here is a parcel of freeform triplets. Freeforms best preserve the pattern and color of the original stone, but they require more manual labor.

Of course the most marketable triplets are those which are cut to calibrated sizes. Unlike the freeform shapes, the final cutting and polishing of rounds and ovals can be aided by cams and jigs. These are perhaps the most common opal triplets.

 Beyond Shapes

It is also possible to create larger triplets, but this is extremely difficult to do without breaking the slices up and producing ‘mosaics’. An artist can select tiny slices and produce splendid pictures, both small and large. and where labor is cheap, designs can be specified so that a large number of stones can be produced.

 Stability and Care of Triplets

Because the opal slice is captured in an air-tight sandwich, using a very fine jewelers epoxy, they are generally not subject to clouding or cracking. However, they should not be subjected to extended periods of immersion in water, nor should they be exposed to strong solvents.

Since the ‘cap’ is made of a hard stone like quartz, should it become scratched, it can easily be re-polished by a jeweler or stone cutter.

Even when the triplet is carefully made, it can happen that the glue either isn’t complete to the edge of the stone, or a separation is caused by some chemical or heat stress.

Here is a picture illustrating what this looks like:

 Grading of Triplets

Of all precious gems, the opal has historically resisted all attempts to create a ‘standard’ appraisal method. There are just too many variables!

Brightness, color and pattern are still the most important qualities, and because the process does not create the fire or brilliance, full-ness of fire and directionality are critical elements.

Dealers typically appraise triplets according to their own experience, and in general, provide a scale of different ‘grades’, ranging from lower quality, all the way to ‘super gem’.

The most wonderful thing about triplets is that they provide the rich deep colors of the most treasured “Black” opal, at a fraction of the price.

This is a story of a few stones from a truly noble parcel of opal, from their discovery, through the cutting process, and ultimately onto the shelves of a fine jewler. There are pictures and movies along the way, as well as a little commentary…

Arguably more valuable parcels have been found, but a parcel found at Mintubi a few years ago is certainly one of the world’s most spectacular parcels of precious opal.

Mintubi is in South Australia, and has long been known to produce dark to light crystal that surpasses even that of Coober Pedy. It is a relatively small area, and in the past few years has all but been abandoned.

I first saw pieces of it in July of 1994, at the same time when the comet was smashing into Jupiter, and I only remember the opal !

I was instantly in love, and quickly bought what I could find, and asked for more. In the next year, I managed to capture just a bit more of it.

I’m not sure just how large the parcel was originally, however I did discover that there were only a very few ounces of the ‘tops’ and ‘keystones’. If I didn’t do something soon, they would all be gone. But the price of the tops was astronomical. Even the lowest class stones in this parcel sold for over $5,000US per ounce.

For someone who won’t even buy a new car, this was not an easy decision. But with those lovely sisters sitting there before me, I hardly remember writing the check !

The Thrill

I would dearly love to be an opal miner and be able to find opal like this, but I have spent enough time there to understand that the chance of finding such a parcel is even less than trying to win the Lottery. But as an investor/cutter, I can still find treasures, and the overall cost is still less than that of mining.

And, there is one joy that only the cutter shares. “Finding” the face and giving birth to a fabulous stone.

The cutter faces many dangers. There’s a great chance of destroying the stone, on the wheel, or by failing to see the best face. And there’s always the chance of cutting into a stone only to find that the sand or clay is so thick that only a few specimen stones can be cut. But there is also the possibility of finding a treasure inside that could not have been seen until this cut !

I like to ‘hedge my bets’ by buying what I call ‘butter’. These are stones that are usually large (over one ounce), but always regular in shape or voluptuous. It is obvious that they are very clean and healthy, and that the material is top quality.

Slabs of Butter

With stones like this, I can cut them like ‘butter’. I like to experiment with different ‘peeks’ into a stone, and by the time I’ve found the best orientation, I still have more stone to cut 🙂

The ‘sisters’ were broken naturally into nice sized rectangular pieces. All were remarkably uniform, about 8mm thick and as much as 80mm long, and 40mm wide. Although they showed brilliant green-to-orange fire on the broad sides, when turned to the edge, they make your heart leap !

As with most of the best material, when I first saw the stones, they had already been ‘skinned’ by the miner. With Mintubi material, often there is a very ‘sandy’ clay skin on the broad sides of the stones, and the miner had simply ground most of it off in order to see the broad side color.

In the stones that had been skinned on both sides, you could easily see that the sand did not intrude into the opal matrix and that the base crystal was very dark but clear . When held to the light, they were clean all the way through, and the pattern appeared to be consistent through all of the stones.

The pattern seen from the broad side is of larger flakes than those seen from the edge. The broad side flakes were really too large to allow me to cut small stones. So, either I had to cut fewer but larger ‘broad side’ pieces, or I had to cut them so that the natural ‘edge’ became the ‘face’.

Cutting from the edge is very dangerous, because you really can’t see what will happen to the pattern and fire as you literally ‘dig’ in to it. But I have had great luck with this technique, and the material really did look to be consistent.

The shape of the stones were very regular, with no ‘wedgies’, and were almost exactly the same thickness. So if I decided to cut the edges, and it was successful, then I could expect to be able to cut a large ‘suite’ of stones, with matched color, pattern, shape and symmetry. This is something like the ‘Holy Grail’ for opal cutters.

No Patience

I couldn’t keep my hands off them, and within a couple of months had decided which of the stones I would first cut, and just how. I would cut them into carefully symmetrical ‘slabs’, with the intention of making several ‘matched stones’.

But first, I had to take off some irregular limbs of the stone so as to preserve those pieces and to regularize the ‘slab’ that would be further sliced up.

After cutting the first little piece from the mother, it was obvious that this was indeed the right orientation for this opal.

It may shock some, but I use a 0.012in. thick saw blade. This may appear a bit thick for such expensive material. But I prefer the thicker blade because it does not ‘wander’. You get a good straight cut, on both sides, and it can be much more economical than if you have to sand off a wavey edge.
One little thing about cutting large stones, is that most often you are cutting right through the best fire. Not only make you heartsick; but the weight loss can be very expensive.

Where did they go ?

After cutting all of the rough that I would allow myself, I put away the remaining ‘sisters’, with no intention of cutting them further until someone who is struck with their perfection, would want some special stones cut of it. And I get the joy of being able to fondle them often !

Just as I am fussy about buying only the best rough, I believe that the best cut stones deserve the very finest settings.

I work only with one jeweler, who has stores in Palm Beach, and Montreal, on streets with Tiffany’s, VanCleef, and Cartier. He’s a masterful designer, and loves the opal. It wasn’t long before almost all of these were where they should be: set in fine gold and diamonds, and in the best showcases.

You will surely want to save the last two movies to your disk and play them back later. You can change the settings of your QuickTime Player so that these ‘loop’ end to end, not forward and back. There is no audio track, so there’s no reason not to play it with the “Play All Frames” option on. If they appear jerky, do this. They will be slower but just as enjoyable. (Provide your own favorite music)

As soon as the wind picks up, the dust blows into every pore of your body, and when it only gusts, the flies come out of the ether to absorb any moisture like from your perspiration, and even from your breath. These flies are absorbing the water vapor coming from Milton’s shoulders.

It can cause a 5 minute delay of operations if the checker or the machine operator ‘inhales’ a single fly…:-)

You can consume as much as $130 per day in fuel, and you may go for days without finding anything, and often decide to give up the claim and find another place to dig. And another creditor or partner !

Given the base line costs of the machine, and the investment, and the labor, there is the problem with physical discomfort and disappointment.

With no wind, you get flies, and dust kicked up by the excavator, but if the wind is up, the dust is choking and unavoidable, and the flies are fewer and you sometimes drop your guard!

Here is what it looks like to be at the face of the mine, looking up at the excavator and the pounding sun…

Kent has had 5 seasons of operating the machine now and is quite competent and even sometimes ‘playful’, best of all, he doesn’t dump dirt on you….!

My job here was as a ‘checker’; one who examines the face that is exposed with each new bite of the bucket of the excavator. What is exposed, and what is pulled off the wall must be probed and brushed and spat upon in an attempt to locate the beginning of a new seam of opal, or the end of one that was pulled down by the last bite of the bucket.

Opal frequently forms in the level, or just above this level, in fractures in the bulldog shale that are caused by shifting of the earth, as well as water and thermal ‘weathering’.

Next is a picture of an older mine which was nearby ours, and shows evidence of at least three different attempts to discover opal in the ‘levels’.

There must have been some initial probe into the area which indicated that there was a ‘level’ here, which showed some ‘trace’ of potch or ‘color’.

Perhaps a bulldozer came in and made a strafing run on the area, causing the widest ‘cut’ feature shown. It’s a toss-up as to whether someone with a pick dug into the wall at the right, or an excavator made the deeper cut beneath the cut of the bulldozer. Note that the vegetation at the ‘level’ is a good indicator of the timing and the extent of each of the attempts that are made by different ‘gangs’ of miners.

It might also be that a very old hand-dug mine (drive) on the right was exposed by the first bulldozer cut and note that it is also along the ‘level’.

This is just a small scale example of some of the opal fields where it is no longer possible to figure out the sequence of these cuts at all.

So there you are, in the hole, eating and inhaling flies and dust. There is no conversation, as the flies love your mouth even more. The only thoughts on your mind are the patterns of cracks and relative softness of the host rock.

There it is !

All of a sudden, there is a very thin line where what had been just red dust in a tiny crack, became ‘opal’. Sometimes this is nothing but ‘potch’, or opal without ‘fire’, but this can be an indication that more precious material might pop out with the next bite of the bucket.

Here is a ‘vertical’ that yielded some very beautiful blue-green crystal opal about as thick as your index finger, but only about 3 inches deep into the wall.

Getting to Coober Pedy

It took more than 24 hours in the air and waiting for connections from Orlando to Los Angeles, direct to Sydney, and then on to Adelaide, so we’re already as far away from Geneva Florida as you can get…

Although Adelaide is a bustling city, it is wonderfully clean and truly deserves the description of a city such as Dallas was in the mid 1950’s.

There were birds of all sorts, and most specially, the desert was in bloom. There were so many flowers, and it was a great thing to just see the green plants instead of the normal brown and dead sticks.

The hiway out of Adelaide quickly turns to two-lane bitumen, and after Port Augusta, it’s two-lane and very dangerous. The Kangaroos are prone to jumping directly into your vehicle, and it’s no joke that many Australian cars have ‘bullbars’ to defend against the chance of a ‘roo crossing paths.

Also, along the Stuart Hiway between Port Augusta and Darwin, it is legal to run what they call ‘truck-trains’. Think of a big 18-wheeler, only three times longer !.

They are limited to 100 Kph, so if they’re running legal, you often have to pass one of them. You gotta build up a lot of courage !

Coober Pedy

On hearing that Coober Pedy probably has the highest number of police officers per capita in South Australia, you might think that this is a dangerous place to live.

In a country where it’s difficult to get permission to own anything but a single-shot rifle, anyone can readily purchase high explosives. And it is not uncommon for someone to get upset and drop a ‘home made sausage’ down your hole, or even bomb the police station or newspaper…

There are miners, families of miners, tourists, and those who serve the needs of the others.

There is a basic understanding among folks here that transcends ‘law’. Anthropologists should study the ‘natural civility’ that has emerged here, where there are very few lawyers 🙂

Over 40 different nationalities, representing most of the races of this planet, co-exist here. Bosnians, Serbs, Slavics, Greek, Italians, Germans, Chinese, Japanese, English-heritage Australians, Aborigines, all others, and a very few ‘Yanks’.

People raise families, teenagers still drag-race in the main street, and still kill themselves. Only the Ampol gas station is open all night. There aren’t any ‘discos’ even for the tourists. But this is the last place you would call ‘sleepy’ or dull.

Folks work hard and play hard here. But everything is pretty well closed down by midnight, as every next morning begins a working day. You can’t be lazy here for very long. The costs are just too high. So every day is a day to mine, or prepare for mining.

There is both a fine public school, and a very up to date college. Only two weeks before my arrival, they had established a local Internet Service Provider. Not that Coober Pedy is behind the times in technology. They already have ISDN and fiber phone lines, as well as a giant wind-driven electric generator.

The town is completely dependent upon the commerce along the two-lane Stuart Hiway, which runs from Darwin to Port Augusta, and upon the regional water wells.

I was amused by the fact that the only day of the week that stood out from the others was the day after the supply trucks arrived at the town’s largest food store. All of the town wives and cooks know to come running.

What is comfort ?

For most of my stay, I shared a ‘dugout’ with Kent. This is a home that is literally dug out of the earth. You might employ someone with a ‘tunneling machine’ to carve out rooms today, but in yesteryear, you would have dug out your home by hand with nothing more than a pick (and a bit of dynamite) !

Not only is this very convenient given the available equipment, but it is also very energy-efficient as the temperature in a dugout remains very comfortable all thru the year.

Kent’s dugout lies beneath the most prominent feature of Coober Pedy, the “Big Winch”. It was originally cut by hand, and only later did someone add the outside rooms. In the inner sanctum, it is more obvious that it was hand-cut.

Although the town is now declared to be a ‘no mining’ zone, it is still legal to dig as long as you stay within your own property lines.

It must be a thrill to be able to dig out a new bedroom for your daughter and discover enough opal to pay for the work and maybe even for some new furniture!

So what am I doing here ?

It was not my intention to be a tourist at Coober Pedy. I had been here for three weeks, four years before. So I knew what to expect, as far as the town was concerned, but this time I would be working in a mine that was ‘showing color’…

I need to know this experience. I don’t think that I will ever be a ‘real’ miner, but I love the opal and I have a deep desire to understand just how it ‘comes’.

I got what I came for, and even more. But my memory is more full of the images of the faces of the towns folk and those of fellows I worked with every day.

My Mates

I worked the whole time with Kent and Milton, getting up early, gathering supplies, driving to the mine, and working at the face of the mine until it got too hot. There were a couple of days that I played hookey and visited other mines, or just washed the clothes.

We ate out some nites, or tried to watch a rental video in an environment where dust is on every surface, and the days became a very pleasant routine.

For the last week that I was in Coober Pedy, I was politely encouraged to sleep at Milton’s home, as Kent’s girlfriend Louise was in town…

My time with Milton was very special, and I cherish the memory of each morning, eating boiled eggs and sipping coffee, listening to the Greek language version of the news, and waiting for Kent to pick us up on the way to the mine.

It is not uncommon to meet folks who have been here for 30 or 35 years, and who have established themselves in the town as permanent fixures.

Some are buyers, some are miners. And the core of the town is made up of folks like Milton Morias.

Many of the miners here have other jobs or contracts which allow them to come here occasionally. Some have been here continuously. It is a disease.

Milton was born in Greece, on Mount Olympus, and came to Australia in the early ’60’s and with occasional jobs as an engineer, he has been mining for the opal as much as anyone. I’m sure that it didn’t take long before Milton became a permanent fixture in this town.

In a remote location like this, it is certainly a great achievement to become known by name in every shop and restaurant.

It’s another thing to also have a reputation of integrity. Milton has both.

And as an aside, he is a wonderfully tolerant teacher. Working with me in the mine, responding to my occasional promts that he look at some ‘trace’ that I had discovered. Sometimes with a grunt of ‘Powtch’ (worthless), and even sometimes with a wonderful “Guuuud Mike !” and I’d quickly move back to let him pick more expertly than I.

Kent

Milton and I were the ‘checkers’, but Kent did all of the ‘delicate’ work.

I met Kent even before Murray. I believe that I met him while he was on his first opal sales trip to the US, and the first three weeks that he was on the field as an excavator operator, I was with him. It seems appropriate that I would be here for the last of his first ‘career’.

He has made a real go of it, and truly has made a number of finds which have not only paid the bills, and the helpers, but have also paid for a great deal of repairs to the excavator and tools for maintaining it. All in all, there’s been a profit to the partnership, but it is very strong statement about the value of the opal, that there hasn’t been any Solomon’s mine found in 5 years.

Back to the ‘ruse’ for this trip:

What does an opal mine look like and what’s it like to work there every day ?