Opal Cutting Video here

The term ‘lapidary’ refers to the art of cutting and polishing stone. Lapidary advice can be obtained on sites like this and also at Lapidary clubs where machines are often available to practice on. Check online in your area to find the closest club, or leave your comments in this blog if you need some help locating one.

How opal is graded and sold

The correct lapidary advice will teach you to grade Rough opal parcels and sort them into three grades: tops, middle, and low. Each tops parcel has a King stone, which is the best stone in the parcel. Some parcels have several King stones. Color is the primary criteria for grading, but the graders also take into consideration the number of imperfections and faults, and whether a stone is the right shape to be cut into an oval or one of the other popular shapes.

You can buy rough opal in several different conditions.

Mine Run. Direct from the mine. The stones have not been cut or ground down. 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. 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 has cut and ground the stones into basic shapes, after having removed most of the rubbish. What you have left is the stone nearly ready for the dopping and polishing process. You have the satisfaction of cutting your own stones without the high risk of buying mine run rough.

Opal is officially sold in troy oz. There are 20 D.W.T. pennyweights to a troy oz. There are approximately 30 grams to a troy oz and approximately 30 oz to a kilo.

Lapidary advice, Hints and Tips

Here’s an eclectic assortment of hints and tips you may find helpful when buying or working with opals.

1. Not all opals is valuable. Potch, sometimes called “common opal” does not reflect colors. Potch does have its use, however, as a backing for doublets and triplets. When there is color mixed with potch it’s called “potch and color.”

2. Some classes of rough opals  are unsuitable for making gemstones. Some are very porous. Others have a chalky appearance. Still others can lose their color in a short period of time. And yes, it is common for certain types of opals to shatter in a dry atmosphere when the water from the gel evaporates. The best protection for buyers is to purchase opal from a knowledgeable  and reputable dealer who accurately details exactly what you are purchasing and is willing to guarantee the stones. Note: If you buy rough opals, there is no guarantee that it will not crack. This is the calculated risk you take and is part of the “excitement” of opal cutting and gaining lapidary advice.

3. When examining opal jewelry, look at the stone from the side to determine whether it’s a triplet. Solid and doublet opal domes are simply the opal formed into a curved dome shape. Triplets have clear crystal domes to protect the flat opal surface.

4. It is very difficult to tell whether a stone is a doublet or a solid if it is in a setting. It helps if the back of the setting is open, but it is still no real indication because the back of a doublet and a solid looks very similar, although a doublet is usually perfectly black on the back whereas a solid black opal usually has some imperfections. So if the back of a stone looks too perfect, you have to be a little suspicious. For this reason it’s best to buy opal from reputable dealers who know what they are doing  and can give you lapidary advice because, unfortunately, many jewelers also are not experienced in opals.

5. When buying opal over the net, ask the seller to give you a summary of how close the graphic sample is to the real thing. Opal is very difficult to photograph and the appearance on the computer screen may give it a different look. Particularly is this the case in regards to size. Graphics come out in all different sizes, usually a lot larger than actual…so make sure you get your ruler out and actually draw the size on a piece of paper so that you will know in your own mind’s eye the actual size of the stone. Here are some examples of rough opal available on this site

6. The same thing applies to the color of the stone. Make sure you get the supplier to give a commentary  on the color so that you will know pretty well what you are getting. The camera sometimes picks up colors that are only minimal, while ignoring the feature colors. Lapidary advice will help you in determining the color.

Cutting Tips and more Lapidary Advice

Lapidary Opal Sanding and Polishing machine

To get all the advice in one book, please consider buying ‘Ordinary Bloke’s Guide to Opal’ in either CD form or e-book form.  Click here for details. And if you would like some details of the opal fields check here

Opal is one of the easiest stones to cut. The trick is chasing the color to make sure you approach the precious opal from the right direction. Lapidary clubs are a good resource for new opal cutters. Ask experienced members for advice on the basics of cabochon cutting.  Mind you, many of them are not familiar with opal so it will be an advantage to have a reference book to turn to

Your first task is to search an opal for any hint of color. Then, you use a wet grindstone to grind off the potch until you can see where the color is going. When you’ve exposed enough color, you can choose the top and bottom for your stone based on where you see the best colour contrasted against the background colour.

Let the stone dry then check for cracks and imperfections. Everyone wants to cut a big stone, but two or three smaller perfect stones are a better choice than one big stone with imperfections.This is good lapidary advice.  Remember too, if you’re planning to make a jewelry piece, settings come in standard, calibrated sizes. Unless you’ll be making a completely custom setting, you’re better off sticking with a common size. A diamond blade, 10 thousandths thick is a good choice for cutting an opal stone to size. Many lapidaries will tell you to run the diamond blade slowly with opal. This is a big mistake. Opal is not a hard material like agate, for example. Opal slicing is best done either in water or with water passing over it at the speed achieved from an ordinary 1440 RPM, 1/4 H.P. motor with a 6″ pulley on the motor and a 1 & 1/2 pulley on the shaft. If you don’t force the stone and you have plenty of water passing over it, you will not cause any damage. In fact your diamond blades will last longer because they will not buckle as easy. After you’ve cut the stone into the basic shape, use a wet grinder to finish shaping and remove rough edges.

The final bit of lapidary advice we can give you is in the matter of sanding. Begin sanding with a 320 grit paper. If the paper is new, you may rub it on some potch* or a sheet of glass to dull its sharpness a bit. You can then use either a 600,700, or 800 grit wet and dry sandpaper to gradually take out the finer scratches and bring up a matt polish. Finally, on a leather lap, use a paste of cerium or tin oxide (mix with water) to bring up the final polish. Your finished opal should have a nice, high dome for easy mounting.

Save the chips! You can use those bits of opal to create stunning mosaic patterns.

If you have a piece of opal jewelry that has become scratched or dull, just use the finer papers (700 or 800 grit) you can try to work the above process by hand by cutting small strips of the sandpaper and just rubbing them back and forth across the stone until the scratches are taken out. If the paper is too harsh, just tone it down by rubbing it on a piece of glass. Next step is to get a piece of old sheet or pillow slip (cloth) and vigorously polish with tin oxide or cerium oxide.

If you want to polish the gold or silver at the same time, use some metal polishing paste. Most of these items can be purchased from the hardware store, with the exception of the oxides which may only be available at Lapidary supply stores or at workshops that polish gravestones.  For Stone masons, check in your yellow or pink pages on the telephone directory for locations.

*potch is unformed opal

Lapidary advice for cutting, polishing, and repairing opals is extensive on this site. Keep in mind that there is a CD available (now as an instant eBook if you want to get a really in-depth knowledge of the subject. Click here for this information.

24 Responses to “Lapidary Advice for cutters and repairers”

  1. Nila Sari

    Hi Peter,

    In your hints and tips you said:
    “…it is common for certain types of opals to shatter in a dry atmosphere when the water from the gel evaporates.”

    Can I please ask, what kind of opal can shatter more easily than the other(s)? I also heard that opal can break /shatter if exposed to sudden temperature difference. Is that true?

    Many thanks,
    Nila

    Reply
    • Peter Brusaschi

      Nila, I have never had such a thing happen. Of course, opal can be shattered or broken but usually when you either drop it on concrete or break it against a brick wall or something hard like that. There are some unstable opals from what are called ‘cracky’ mining areas which will craze or crack after a period of time no matter what, but these mines are generally well known and avoided. If you purchase from reputable dealers, the stones are guaranteed anyway. Hope this helps. Peter -www.opals.co

      Reply
  2. Nila Sari

    Hi Peter,

    In your hints and tips you said:
    “…it is common for certain types of opals to shatter in a dry atmosphere when the water from the gel evaporates.”

    Can I please ask, what kind of opal can shatter more easily than the other(s)? I also heard that opal can break /shatter if exposed to sudden temperature difference. Is that true?

    Many thanks,
    Nila

    Reply
    • Peter Brusaschi

      Nila, I have never had such a thing happen. Of course, opal can be shattered or broken but usually when you either drop it on concrete or break it against a brick wall or something hard like that. There are some unstable opals from what are called ‘cracky’ mining areas which will craze or crack after a period of time no matter what, but these mines are generally well known and avoided. If you purchase from reputable dealers, the stones are guaranteed anyway. Hope this helps. Peter -www.opals.co

      Reply
  3. Herbert Fellows

    Peter, you say that ‘some opals can lose their color in a short period of time’.

    If that is the case, how could you ever know what you are getting? You can only buy what you can see, how could you know that it might go away?
    Is there a specific type of opal this happens to, or is there a time ‘limit’? In other words, if I own it for a year, let’s say, can I be assured that it will retain its color?
    I would hate to sell someone a piece and have the color go away, that would be disastrous!

    Reply
    • admin

      Herbert, can you please send me the url where you read that comment about opal. It has to be taken in context. I have never seen an Australian Opal lose its color in 40 years of dealing. However if the opal stone has been capped with a crystal as in the case of opal triplets, it can lose its color if the wearer soakes the ring in hot detergents and washup liquid every night for a few years. This is because the cement holding the cap on to the stone eventually gives way. There are opals from other countries that may have this problem, but i dont have the experience with that. Another opal that CAN fade, but most unlikely, are opals that have been dyed or treated, but of course these are not natural opals. But just remind me of where i have made that statement in case there is an aspect i have forgotten. thanks for the question Herbert. Incidentally if you want to do some opal on-selling, please contact me direct by leaving a message here: http://www.opals.co/contact-us/ Peter

      Reply
  4. Brad

    Hi Peter:

    Two questions, if I may. 1) in your photo you have two wheels- what grit level do you have on them?
    And, 2) do you hapen to know the grit level cirium oxide that you use is equal to? 50,000 ? 100k ?
    Thanks

    Reply
    • admin

      Brad, if you are using carborundum you can start off with 220 grit and go to 320. diamonds you can start at around 100 and go to 600, then on to the rubberized diamonds. let me know if you need further help about opal. best wishes Brad, Peter

      Reply
  5. Larry K. Matlock

    My wife broke the 18mm x 13mm solid black opal from her ring. I glued the two pieces back together, and in reinforcing the bottom, found much more color there than the top, good red fire. How practical would it be to have the epoxy ground off, and a doublet cap glued in its place, to show off the best color? I am in California. How to get this done, if practical, and how much to pay?

    Reply
    • admin

      Larry, its better if you send me some good pics of the stone so i can advise you properly. try to use a camera with macro or close up facility. put the camera on a tripod or on a bag of soft sand and take the shot on a white background using fluero lights. try to control the amount of light or it will be too bright. send the pics to me by email but reduce them to around 100kb. i will do what i can to help. if you cant do that, better contact me on skype and we can have a talk. will help in whatever way possible. no obligations. best wishes Larry.

      Reply
  6. Jo

    Hi,

    Do you know of the closest lapidary club to Airle Beach QLD 4802. Many Thanks

    Reply
  7. Joseph Stevens

    Have some opal I purchased in Australia over 20 years ago. Would very much like to do something with it. I live in Mena, Arkansas. Attached is a not so great picture, I am not very good with the camera. Please advise if you know where I may be able to take my opal and either have it worked or gain assistance in learning how to work it myself. Thank you for your advice.
    Joe

    Reply
  8. FRANK WESTRIP

    Hi peter I have just watched your demonstration and may I apologizes for wasting your time, The stones I have are very small in comparison to your demonstration film and am sure there is very little value in what I have, but as I have taken the photo’s , I won’t be upset if you do not reply me this.
    regards Frank
    P.S. where abouts are you in QLD ??

    Reply
    • admin

      No problems Frank. will always do whatever i can to help. it doesnt matter how large or small your stones are. unfortunately the picture doesnt tell us much because its not clear enough. you need some really close up shots with a macro digital camera. please go to this article for some information on photography. hope this helps.

      Reply
  9. M. Dobesh

    I have my late sister’s Mexican opal ring. It is of little value I believe, only sentimental. Its “fire” has been dulled do to some abrasion, as if she might have tried to clean the silver ring and the silver polish dulled the stone’s surface. I live in rural Baja, and have no local jewry store for help. Can you suggest something that I can do to restore the stones luster?
    Thank you,
    Martina

    Reply
  10. M. Dobesh

    Please help, my late sister’s Mexican opal ring has a dull finish, because I used a silver polish and made the mistake of also applying it to the Opals surface. Now it is dull, having taken the luster. What can I do?

    Reply
    • admin

      Martina, i just answered you by email. I think you said that your post on this program didnt work but it seems to be here ok. anyway check your email for further advice about your opal problem. Peter

      Reply
    • admin

      Dear M.Dobesh, sorry, i didnt get your first name. you need to get some cerium or tin oxide from lapidary supplies. just look this name up in google and see if there is a lapidary supply shop in your area. you can also look up Rock Hounds. mix it into a paste and rub it with a piece of cotton cloth. if there are no scratches in it, the shine should come up again, if it is genuine opal. Hope that helps. Peter

      Reply
  11. javad

    سلام امکان ارسال سنگ به ایران هم هست ونحوه پرداخت پول ان چگونه است

    Reply
    • admin

      translation into english: Stone is also possible to send greetings to Iran to pay for how motion is answer in Persian. متأسفم. من سوال شما را درک نمی کنند. لطفا به من بگویید، آیا شما می خواهید چیزی در مورد اوپال استرالیا می دانم؟ از پا افتادن Peter – Is your question about opal?

      Reply
  12. Sylvia D

    Hi, I have opal earrings bezel set in 14K gold. I noticed the glue used to set the opal triplets has released from the edge of the bezel so I am afraid of the opals falling out. What would you suggest? Can I use superglue, ie: Maxi-cure? Thank you for your time. Sylvia

    Reply
    • admin

      Sylvia, regarding your opal earrings. Best idea is to get a good shot of the earrings and send it to me via the email marked in red on front page of http://www.opalmine.com i can then see whats going on and advise you. best wishes Sylvia. peter

      Reply

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