Cutting Ethiopian Opal rough
Ethiopian opals are cut and polished in a similar method to most other opals.
The exception is Ethiopian opal which is Hyrdophane, that is it absorbs water. So more importance must be made in selecting and sorting or grading the Ethiopian rough.
All rough should be fracture tested before cutting and polishing or you could end up re-cutting a stone with crack in it.
One popular method is to use blunt metal object like screwdriver with end blunted and use rubber mallet to tap suspect areas.
This will result in cleavage on weakest point of the crack, you might end up with several pieces but they should be stable after this.
Another method is water treatment, by adding water from cool to warm water, that will help to expose cracks and make sure you dry out the opal completely.
Fracture testing gemstones has been common in gemstones such as quartz for centuries.
All major carving centres of the world fracture tested rocks before carving as very time consuming.
Set opal on your dob stick using glue is better than heating Jewellers wax for Ethiopian opal
Then shape and polish the opal and enjoy the display of colours after you have finished polishing
Tricks to learn when Cutting Black Opal.
Black opal mined at Lightning ridge is cut and polished similar style to all other opals .
The most important aspect of black opal is to determine which side of opal to cut.
This may seem basic information but it is the most common mistake cutters make.
After purchasing parcel of rough opal, never cut the most promising piece rough opal.
Always start on small pieces so you understand how the opal will cut.
Start by rubbing small corner of piece to determine which side faces the best.
Some grey rough will have black centre so also rub on grey pieces before you start on black.
If large pieces crystal opals they will sometimes cut better display colour if cut at angle.
It is a lot of trial and error and no set rules with rubbing black opals.
Except use common sense when cutting black opal.
Cut small pieces and understand how the parcel will cut.
Even on the opal fields some opal mines will vary on composition on each layer as opal mined 20 feet down might be different o opal mined 40 ft down.
Another problem new cutters find is that their new polishing wheels are to Sharp and rub away the thin colour bars on black opals.
I have seen $800 parcel rough cut with sharp grinding wheels and only cut $200 a s colour was rubbed away.
With new opal cutting equipment it is always best to rub large rock or piece potch against new grinding wheels 80.120,600 grit,actually any new diamond impregnated cutting wheels should be worn in before any serious opal cutting is performed..
Opal cutting equipment can be home made or purchase commercial opal cutting equipment .
Essential Cutting tools:
Trim Saw with thin
Strong glue or Dop wax
Diamond grinding wheels ranging from 80, 220, 600, 1200, and 3000-grits
Blade (with rim thickness approximately. 0.02")
Lamp (with 100-watt bulb)
Tin Oxide Polish
Old work clothes
Many cutters do not use enough water while cutting and polishing boulder opal
How To Cut and Polish Boulder Opal
First pick out days work of opals you wish to polish and set on dop sticks.
Australian boulder opal from Queensland is considered a fascinating stone. Cutting boulder opals is considered challenging. Consider the following steps below:
Two options for dop sticks Glue on dop sticks or use jewellers wax and melt opal onto stick
If you not sure which way to polish and opal try an off cut or small area first
Never cut best stone in parcel
Always do expensive opals last when you understand how the parcel will cut
Always have strong water pressure when cutting. Dirty opal Apron worn by Patrick and Lapsia added to polish wheel .
(A)-selecting boulder opal has its own exceptional concerns. Like any other rough, the further you know the better. In fact, there are some few tips to consider. If you’re still undecided, you may ask dealers for better suggestions for looking economical rough that will be fairly simple to cut.
Then, make sure that the ironstone around the opal is fairly strong. You must be aware with some deals that mostly too good to be true. Sometimes, some reasonably low-grade material is good to start with. You might not end up with a beautiful stone exactly, but you can develop your systematic skill enough that you will be capable to cut that attractive stone in any way you want.
(B)- look for a flat, rough Opal flat and check at the grain as well as, the pattern of ironstone to provide you some clues about the path in which the seam will run. Once the opal occurs in ironstone, it illustrates quite flat and straight parallel lines along the matrix; so there is a better chance that the opal will track this line.
Saw blade should always be under water and spitting out volume .Never cut dry as opal will heat quickly
However, if the ironstone displays some rounded lines, of course, the opal will somewhat look like a slightly curvy. You can check for the cracks. Keep away from rough that has been saturating in glycerin or oil, which are both hiding some cracks. If the rough is soaked, let it dry first. While you are discussing to the dealer, then you can check for the flaws. Then, some pieces of rough may be moderately faced.
Hence, the ironstone has been ground down to represent the opal layer. This can rather provide you a better idea of what you are purchasing and accumulating, but you need also to ask yourself why most of the dealer selling this instead of cutting it, accordingly. Please be avoided any faced material that has deep gashes within its opal layer.
(C) this step involves preparing the rough and utilizes some set of old clothes. You'll be presenting something like fairly a bit of brown mud with stains. If needed, check the excess ironstone in order to control the outstanding piece of rough through the use of trim saw. See at whatever line of opal is perceptible as well as, the pattern of the grain of the ironstone.
In addition to, try to calculate the course in which seam will run. Having a combination of 80, or 220-grit wheel can help either to describe the borders or the line of the colors. Also, try not to get even closer to the line of opal. The layer of opal can cause some unanticipated turns, which you can damage, especially the saw blade.
(D) -with this step, you need to check back the wheels, clean-up the stone frequently, and checking for the opal. As soon as you find one, discontinue, and rotate the rough to get other edges of the opal. You’ll need to make sure that the 80-grit wheel does not tap the opal because it can be harmful.
Once you have found the edges, check cautiously the shape of the line as well as, the setting of the ironstone on either surface of the line in order to establish how to familiarize the stone.
(E)in this phase, it is significant to familiarize the opal. You must decide which surface is going to be the top. Base your judgment on the form and layer of the opal, the coloring, potency, and width of the surrounding material. If the row of opal is rounded, it will typically be easier to slice, especially if the top of the stone is in the convex form and the base of the stone is in bowl-shaped along its side.
Basically, the material that is directly below the line of opal must be dark as much as possible. This dark setting will create the colors of the opal to be stand out. Also, there will be a thin cover of black potch between the row of the ironstone and opal. You must try to cut the stone so that this black coating will give the backdrop for your stone.
This kind of stone is referred as a black boulder and opal boulder black and can be quite radiant. It is also significant that the boulder opal consists of a solid base. If the ironstone on other surface of opal is too lean, it will not offer the potency that is needed for the bottom of your stone.
(F)- the sixth step involves exposing the opal. It begins with the 80 or 220-grit wheel, which is use to eliminate the ironstone and covers the peak of the opal. It is an ideal to use, especially for the ironstone layer that approximately measures 4milimetres wide. When using the 80-grit wheel, be cautious and apply the light pressure.
Moreover, it can cause chipping or create deep grooves. When eliminating the ironstone layer, be alert and apply water, as well. Time after time, prevent and wash off the face of the stone to ensure for the exposed opal. In fact, the layer of the opal can get surprising turns or prominence from some unanticipated regions.
(G)- as you getting closer to where you consider the opal is; consider using the 220 and 280-grit wheel. You must strive not to come into get in touch with with the opal once you decided to use the 220-grit wheel, as it can rapidly eliminate quite a bit of vibrant materials or begin with some serious gouges.
It is also advisable to use light pressure ranging from 220-grit wheel as you getting closer to the opal. You must keep on eliminating ironstone until you just about display opal in one part of the surface, or at least until you are getting closer to the opal layer. Occasionally, before you reach the opal, you will even notice that the color of the ironstone will change.
(H)- control the 600-grit wheel in order to expose some opal. At this period, you are not trying to eliminate all of the ironstone from the surface. You can do it by going back and forth between the 600-grit wheel, by having medium pressure, and by means of 280-grit wheel using light pressure. Once you establish how the layer of opal operates, you can stop working on the top.
Cutting Australian Boulder Opal Rough:
Cutting thin colour bar always go slow and use rubber wheel when colour shows ,Do not rub hard.
Once you have a better idea for the nature of the opal, use light pressure on the 220-grit wheel or an average pressure on the 280-grit wheel to form or eliminate any irregularities from the border of the stone. This nature will not essentially be the absolute form of the stone, but it will almost certainly craft the stone easier to work with once it is on a dop stick.
Meanwhile, some boulder opal, particularly with high-grade material needs a machine in several cases; especially some attractive stones that can be cut effectively using diamond wheels. Check the following steps below:
Dop wax or strong glue
Trim saw with thin
Blade (with rim thickness approximately 0.02")
Diamond grinding wheels 80, 220, 600, 1200, and 3000 grits
Tin oxide polish
Lamp with 100-watt bulb
Old work clothes
Polishing wheel start 120 grit diamond than rubber wheels 400 grit 600 grit 1400 grit before last polish
(A)- when doping the Opal, use the 220-grit wheel by means of 80-grit wheel, you must set up the stone for doping by flattening its reverse side. Then, trim down the width of the back of the stone so that it is just somewhat thicker than what you consider as well as, that would be suitable for the completed stone.
Smoothly put the rear side of the stone beside the 80 or 220-grit wheel, while rotating it along your fingers. Keep in mind, you are pulling down the back, but not cabbing it. In fact, the rear of the ironstone usually measures more than 5 millimeters wide, unless the stone is quite big or has a remarkable shape. It is significant to verify that that the rear side of the stone is broad enough to sustain your opal.
(B)-from here, the stone is now equipped to be doped. The base of the stone must clean and dry. Sometimes, applying one or two drops of glue to connect the dop sticks is necessary. Also, pre-heat the opal by resting it on the border of the dop pot for not more than 30 seconds. After polish, infuse the opal through the use of warm water to eliminate it from its dop stick.
Then, use light pressure to burst the opal into dop stick after about 30 minutes. It may or may not approach off, but you may require soaking it overnight. If the reverse side of the opal is spongy, you may use dop wax as an alternative to the glue. In such cases, you must eliminate the opals from their dop sticks by putting them in an open bowl.
Moreover, you can put the bowl in the freezer for about 5-10 minutes. Take out the bowl from the freezer and watchfully set the blade of a knife along the line between the base of the stone and the dop wax. Apply moderate pressure, and the stone must pop off somewhat easily.
(C)-this is the step where you can cut the opal. If you’re using a device that re-circulates its water such as the water that sprayed up onto the wheels, you can dripped down into a pan, then forced from that pan and sprayed up onto the wheels once more, change the water and make the pans dirt-free regularly.
In fact, large pieces of ironstone and opal that were eliminated within the 80 and 220 grit wheels can display onto the 280 grit wheel, which can cause scratches. This is really proven, especially with the set of finer wheels. Several stones using the 80 and 220 grit wheels can change the water.
(D)-once the glue has dried out or the wax has cooled; consider about its natural form, which might not be the form you desire it to be. You may use the 280-grit wheel with light force to eliminate some serious scratches from its border and the top. It is also significant to keep the stone moving to avoid flat spots and scrapes, as well.
Stop often and clean your stone to check its development. Check the face of the opal, not into the opal. After performing this, use the 600-grit wheel to eliminate the scratches caused by the 280-grit wheel and to describe more of the opal.
This is the form of boulder opal. It is also need to consider when eliminating them totally that would rigorously deform the nature of your stone. In fact, these distinctive patterns will add traits to your stone.
(E)at this point, you require to make some significant decisions. Look at the general appearance of your stone, both the ironstone and opal. Their combination can be relatively beautiful. If you are not pleased, most of the complicated work is ended. If not, you will feel that there is more wealth lurking under the ironstone.
Keep on eliminating ironstone with the 600-grit wheel; think about keeping the stone moving. The 600-grit wheel can still reduce opal and create smooth spots and scrapes. You can do a lot of things during this stage of cutting. You are eliminating scratches from previous stages.
Then, eliminating ironstone from the surface, and building the surface and form of the stone is pleasing to the eye. Check your stone and observe what it shows you. You might require checking back the 280-grit wheel and changing its form. Once you have eliminated the big scratches and are pleased with the look, go to the 1200-grit wheel.
(F)- in this step, the 1200-grit wheel will eliminate almost all noticeable scratches. It will not do much to modify the form of your stone, but it can get better its form. Use reasonable pressure and maintain the stone moving. Make sure to cover up the complete stone, including the areas and surfaces of ironstone.
Stop regularly and clean up your stone verify the progress and ensure that the scratches are completely vanishing. Though the effects of the 1200-grit wheel are not right away, clear those with the 280 or 600-grit wheels. In fact, the 1200-wheel is also helpful to round any pointed edges.
Once you have removed the noticeable scratches, shift to the 3000-grit wheel, or if you’re not using a 3000-grit wheel, begin to clean your stone. If your device consists of a 14,000-grit wheel, it is advisable not to cut boulder opal. This wheel begins often with scratches.
(G) – the next pace is the process of polishing. In order to make it shine, you can use tin oxide for cleaning the foam-backed rough leather pad. Just lightly soaked it with water through the use of a spray bottle and with the running device running and spinning pad.
Also, use a brush to apply a well-stirred combination of water and tin oxide onto the moist pad. From here, the water mixture as well as, the tin oxide must be thin enough so that it does not clomp, and has the uniformity of thin gravy.
(H)- choose a dopped opal to be refined and either softly touches it to the polishing pad so that it selects up some polish or just taps it with the brush through the use of water mixture and polish. Use a light to temperate pressure then, clean the opal on the pad.
Just keep the opals stirring by turning the dop stick between your fingers and by varying the position of the pad, as well. Check also the development often by lightly wiping the face of the opal. Consider to clean the edges of the stone, as well. Maintain a rigid hold on your stone and do not use too much force.
Do not allow the opal to get too sizzling. Sometimes, the coarse leather pad can seize your stone and pull it out of your hands, mostly as the pad dried out out or if the stone has a rough surface or even pointed edges.
(I)- from this phase, it takes observation to establish when you are completed cleaning an opal. If you preferred to eliminate all the scratches as well as, make the opal as vivid as possible, maintain the pad soaked and reapply the water mixture and polish, as well. If the pad gets too waterless, it can cut the opal or it can cause it to be overheated.
If your opal has consists of ironstone along its surface, or if the surface is mostly spongy, you must be cautious. Often the leather pad will seize on the ironstone, or either you will feel a yank from the stone, and the pad will break into tiny pieces that could spoil or cut your opal.
Lapsa Powder brushed onto felt or pig skin gives good results. Note opal cutters brush
(J)- if you are decided to polish a matrix opal, you can pursue the same process. The opal usually polishes, but the ironstone matrix will be dry. A helpful method is to clean the opal as explained, and then permit the pad dry faintly. Use more force while you maintain the stone moving, so that you can sense the stone to get even warm.
Remember that you are cleaning the matrix, not the opal spots of your stone. Be careful while heating the stone along your polishing pad, which can develop the finish of the matrix, but be, reminded that too much heat can break the opal. This method needs a bit of practice, but the outcomes can be worth it.
(K)- this is process where you can do the finishing of the back. When you are completed polishing, eliminate the stone from its dop stick. You can use light to standard pressure for roughly about 220-280 for your grit wheel in order to take out any residue of the doping matter.
You must keep the stone flat against the wheel, but turn it slightly so that scratches will be avoided on its back. At this point, select what you prefer for the specific size of the stone. When you arrived with the suitable thickness, apply the 220 or 280-grit for the wheel that can be help to minimize chipping when setting.
Depending on the manifestation of the back and your taste, you can either think the opal completed, or get a more finished look by checking the back through the remaining chain of finer wheels. You must regard the back portion of stones by means of 1200 or 3000-grit wheels.
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