Cutting Opal from the rough into a finished stone is very rewarding. But as a beginner it can seem daunting to figure out what type of Opal rough to choose. Lets take a closer look at some of the options.
First you will require Opal cutting and polishing equipment. A basic saw blade and different size polishing grit wheels from steel to rubber impregnated with diamonds in different grades and a polishing wheel.
Mixed parcels of rough opal around $20 to $50 are good to start from Koroit, Ethiopia or Coober Pedy rough. Ironstone with good patterns from Koroit and Yowah opal rough are good to learn polishing as if you polish to hard you wont rub away opal color. Yowah nuts are rock shaped and have strong colors but it is said only one in thousand has any color.
Ethiopian rough Opals has thick color bars and good value as it is inexpensive to purchase, so start plain patterned on first purchases and inform yourself about hydrophane properties of this opal especially when polishing in water.
Boulder Opal has many thin veins of color and can be difficult to polish with new wheels as many cutters will rub lot color away trying to obtain a good finish. Boulder Opal Rough also needs to be split sometimes by placing saw cut so rock split opens.
Black Opal rough from lighting ridge can be very tricky. Black Opal rough comes in two forms, seam Opal or Nobby Opal. Seam Opal is formed in layers and is best to learn on as color bar sits on bottom potch. Most this potch is grey in color and has body tone N4 to N5 and opal needs body tone N4 and above to be classed as Black Opal. Most Black Opal mined at Cochran is called Nobby Opal. This opal can be expensive and is formed like rock with color bar and can be difficult to read how to cut and polish. Many cutters make mistake of rubbing down the wrong side so when purchasing parcel always start off with cheapest pieces to see how the color faces. Even try cutting on angle to expose the best fire color, clarity of color is more important than size with good Black Opal. Many opals cutters will say they break even or loose on half rough Opal they buy but do well with the other 50%.
So when buying Opals that show color bars only you might think why hasn’t the miner rubbed it away? So veined rough has to be viewed a s gamble purchase, but win or loose it is still fantastic hobby to cut and polish your own opals and set in jewelry for family and friends.
The parcel below displays a lot of blue to green color in crystal. All opal miners look for nobbies for color formed on potch. Potch is basically opal that is one colored ie just white, just black etc. It is the most common type of opal what we want to find is precious opal that display many colors. Some of these chunks will display opal bars but difficult to check when in this rough condition. Larger pieces are saw in two on a rough cutting wheel so to expose any color.
New opal cutters are best to start with boulder ironstone or Koroit opal rough. Alternatively Ethiopian Rough opals is still reasonable price at present and as the crystal color bars are thick, it is good for new cutters.
Once you have cut a few hundred opals and have good polish with no scratches than best to buy boulder opal rough with thin color bars to see how good you can rub down and keep as much color as possible.
Some Black Opals may contain shells or fossils and these are best not cut or polished but left natural. Coober Pedy has more fossils and shells and these have been popular as inlay rough material or for making doublets and triplets.
Experienced cutters can than purchase Black Opal Rough as parcel lot. As with all rough it is best to cut the most promising piece rough last not first! Many cutters are keen to see what the Rough Opal will expose but its always best to do smaller pieces so you get better feel for the parcel. This is not as easy as it sounds as most opal factory’s use expensive ultra sonic drills.
Diamond tip drills are now relativity inexpensive but a cutter needs to take care when pushing drills through to other side (especially when trying to make beads) as a hole needs to be made from both ends or opal can chip.
Rough Opals conceal dazzling beauty, a hint of which is revealed by dipping the stone in water (as the sellers do; your rough opal(s) will arrive dry). A basic saw blade and good polish are essential to revealing the beauty of a rough opal, as are patience and time. If polished correctly, some opals reveal a bright fire color. These dazzling color bars can be rubbed away if polished too roughly.
Opal-cutting lapidary machines are available for purchase but may not be necessary if you can make your own.
Rough Opal can be sourced direct from opal miners and wholesalers/dealers. It is available from all the major Australian opal fields:
Ethiopian rough opals was hard to obtain as the government will ban exports of Ethiopian rough mid 2013.and only allow cut stones to be exported.but they have now changed this policy but have high tax on exports.
I have seen many new cutters go straight out and buy parcel rough black opal and start cutting. Unfortunately they rub lot colour off trying to get good polish. This is due to 2 reasons firstly experience and how to polish and also most cutters have new wheels and don’t realise how sharp these diamond tip wheels are and leave big scratches in the opal so when polished the colour bar is rubbed away.
Best is to start with rough opal from Koroit opal rough or Yowah opal rough, or Ethiopian rough just middle to low grade opal rough. This is easy to polish as you don’t have to follow colour bars .it is messy and brown stains but you can tell when polish is good on the opals.
Next is to try cooper Pedy white opal rough as they have thick colour bars and to rub down, than go and try boulder opal rough or black opal rough with thin colour bars
Remember to always rub the worst looking rough in parcel, never start with the best promising pieces of rough, pick out the best looking rough opal and leave it aside than rub and polish the lower grade, this helps you get the feal of the parcel and sometimes cutters get top and bottom mixed as experiment on low grade before you cut the good opals
Buy volume parcels and get experience, if diamond wheels too sharp just try rub down smooth with any tough stone and make sure you rub down even and have plenty of water
Semi black or grey rough is good to start for lightning ridge material and sometimes these centres are black so if cutting these go for smaller black opal instead of large grey based opal
Today the best way to buy opals is to buy on internet or go direct to opal fields of Australia and dig your own opal. In past opal miners and opal wholesalers would visits shows like Tucson in USA but today these shows are so expensive to go as seller. Booth and travel costs are well over $20,000 now, and that’s only for one person. Now opal miners and opal dealers prefer to offer you opals at wholesale prices from the internet. So make sure you buy for opal dealer with good feedback and who stand behind their product. Most opal miners and opal wholesalers are honest and hard working, and have genuine passion for opals.
Ask as many questions as your comfortable with as to where the opal came from and ask is image accurate picture.
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