Engraving opal


#1

I only just got my glowforge setup yesterday so I’m not exactly an expert in it’s settings yet. I have to say that it’s the quickest machine from unboxing to actually doing something with it of all the 3D printers and mills that I’ve spent money on. I am very happy!

There has been some discussion in the boards on engraving various unusual things like semi-precious stones. A friend of mine cuts opal and was very curious about the possibility of engraving designs or just figures over flaws in the stone. So one of the first experiments I had to run on it was trying to engrave some opal!

It’s mentioned several times on this forum that opal has too much water as a part of the matrix and that it would just blow apart or crack. Thats always a danger with Opal and if your settings are too high then I have no doubt that you could crack or craze or destroy it, but my initial testing turned out very nice. I’m not happy with the resolution but it actually looks quite nice.

I took an unpolished piece of sub gem quality, white matrix, opal with a very flat face and attempted to place my initials on it. These are 2 passes at 35% power. The stone is actually etched, not just discolored. I can clearly feel that it’s etched slightly into the stone and not just discolored it. I think it would look quite nice if done more artistically than I can do with just burning in my initials.

There are issues of course. I don’t believe you would have any hope to actually cut opal with this laser. I don’t know what it would do to a truly gem quality piece, or if this one was very dried out, or if the curve of a nicely polished piece would give it trouble. So don’t do this to a multi-thousand dollar gemstone quality piece without a lot more experimentation. But I know there are those here who would love to see the picture.


#2

Sometimes white on white stone engraves don’t wear well. Try getting it wet or dirty with finger oils and see if your contrast stays, You might also see the engraved surface start to spall and flake away in some cases. It looks great as is, but longevity can be a concern.


#3

That’s a great effect but I wonder if anyone else cringed at the title? :smile::wink:


#4

Opal is a naturally hydrous mineral, so the water content can be problematic. Some recommend storing gem quality stones in glycerin, some like to dry them out. I have cut pounds of the stuff, my favorite stone. I kept mine dry, but I have seen some craze when they dry.

Relatively soft, 5.5-6.5 Mohs scale so I’m not surprised it etched. The ‘Queen’ of gems, it developed a rep in the middle ages of bad luck, because if the jeweler broke it, it was his nickel. Several times I had a beautiful cut stone, made the setting and had it crack at the last tightening of the bezel.
Ever seen a grown man cry?
Cool that it can be done, but to my mind, it covers the fire in the stone. Stuff is a joy to cut because you are cutting through the layers of fire, and don’t know exactly how the stone will present until the polish. Always a surprise!


#5

Please keep details like that to yourself, I do NOT need another hobby. :wink:


#6

Yes I have also cut and carved many pounds from many sources, the sensitivity to drying varies widely. I carved a very nice little horse out of Honduran opal that was very sensitive and decided I would rather have it put back with cyanoacrylate glue than toss aside a half made piece. in the end, it broke ten times or so and had to live out its life in a jar of water, as it would just be chips if allowed to dry out.

By contrast, most Australian Opal is very stable but I still store all the unset stones in thin neatsfoot oil as the fire dies down in even the most stable stones but heat is the enemy of all opal, and I would not even dare to size a ring without unsetting the stone.


#7

Yes, I found Coober Pedy material to be stable, but I have seen some lower quality from Nevada that when you pull it out of the ground and hold it to your ear you could hear it cracking.
Such a beautiful mineral.
Down the thread a bit is my all time favorite opal, Bad picture, but it looks like turquoise from any distance until you get close. Only example of a homogenous single color I ever encountered.

Edit; I see you already liked that post…


#8

I have a few pieces of Blue Opal, not a lot of fire but of little need of it, as the base stone is a powder blue. found in one mine in Mexico I was told and not much. I knew a major wholesaler in those days and got several one of a kind or ver6y rare stones, and I bought all the blue opal he had left, and have never seen similar since.

Yours is also gorgeous, and as is the same with most each stone is very individual. I had one piece that the matrix was like powder you could brush away with a toothbrush and what was left was very firey opal. I used carving tools to polish most you could see but it looked like it had been heavily eaten by termites, and was called supposedly "termite Opal. I have searched a lot but never saw another piece.


#9

Looking now with internet advantage I came across this, Hinting that it is possible that it actually was termite eaten wood that became fossilized as opal.
The raw stone was sold very cheaply because the matrix was so soft but with a bit of work it was really amazing .


#10

I never saw anything like that…
How do you dop your stones? The wax never worked for me, I would lap a nailhead flat, and use CA glue. To remove the stone I would clamp the nail in the Panavise and hit the shank of the nail with the oxy acetylene, and as the heat traveled through the metal, with a little pull by hand the bond would break before any significant heat could be transferred to the stone. Rock solid dop.

The fire in that specimen in your picture would inspire me to work with it any way I could.


#11

The one I had had a lot more fire actually much like the outer edges but no part of the stone was as thick as that one closer to the size of the outer edges it was a lot of wires and thin bits hanging out alone. What struck me with this one is the outer skin is very similar as if there was no real matrix and it was just a matter of smoothing and polishing the bits that I could reach.


#12

For the uninitiated, ‘Dopping’ in lapidary is putting a handle on the stone you are cutting. Cutting is done on a wet gringing machine like this…

@rbtdanforth, I have had such a beautiful nugget that I couldn’t bring myself to cut it - I just polished that thing as is. You can get lost in the layers and color of that stuff, and just stare at it.


#13

I have some square green sticks of dop wax that I bought several sticks, gads! 55 years ago or so and never used up as I would use it over and over. on several sized dowels. I also had some clear yellow wax that would melt at a much lower temp and I would use it on such stones as would not be injured by the heat. If you heat the stone and put the cold dop stick on it I never had a problem.

For Opals, however, I would mix epoxy and lamp black or just buy black epoxy and glue the stone to the stick. then when I finished polishing it I would saw the stone off the dop stick and grind the back a bit till ant leftover dop stick was gone and let it go out that way.

The black epoxy would absorb any light bouncing back through the stone and brightening the fire considerably… This was commonly done in Mexico and I adopted the practice as the stone’s weight mattered almost not at all in the pricing but only how much fire was there, etc and it also strengthen the stone after it was stet.


#14

Fascinating to listen/(read) in on a bunch of expert enthusiasts in their field. (Even if you’ve got no clue what’s going on half the time.) :slightly_smiling_face:


#15

Oh but the really cool thing I found was some wooden pegs made to glue in a board to make a place to hang a hat or jacket, They had a knob at the end and a narrow waist that was perfect for holding the stone while cutting and having your hand at the other end with perfect for control as it was twisted and rotated to cut the cab evenly plus they looked very good also and were varnished except where the peg went into the plug and thus perfect for a thin layer of dop wax on that part that came even with the shoulder to finish out the clothes peg. I probably have them here somewhere still but everything is still scattered and a disaster since moving a year ago. Like this but just the pegs

I suspect that your issue might have been not letting the dop stick grow cold and heating the stone enough to melt in a layer of dop wax, then whwn you are finished just heat the stone again and it will come off cleanly. The operative word of course is heating the stone and as noted there are some you do not want to heat.


#16

Interesting how we adapt our own methods.
In finishing, my technique evolved to the final cut graduating to 1500 from 320 with a piece of wet or dry (wet) in the palm of my hand. The paper conforming to the soft curvature of my hand for a perfect dome with no flats.
Glad to meet a fellow enthusiast! :sunglasses:


#17

Better stone than Glass, I knew a guy who was making $30,000 each for his works but lost 80% of them just staring at how nice the piece was turning out when it was a few seconds too long and !CRACK! the piece was suddenly worthless trash, He quit making them to save his sanity and made other things,
This is one of those pieces, every tree leaf etc was put on with a torch while not letting the glass get too cold


#18

Hahaha! Reminds me of a story of Leonardo, after working for years on a lifesized sculpture of Mary holding the body of Jesus, he attacked it with a sledge.
Artists. They’re dangerous people.


#19

i bought a few pieces of finished Turquoise from a couple that the guy was a long haul truck driver and his wife was basically along for the ride, and so bought raw turquoise and cut them from start to finish that way.

I had a girlfriend who claimed to be psychic and explained that the more the person interacted with the rock the more the rock would absorb the person’s "energies’ so I dumped 50 or so cut turquoise stones on the table and asked if there were two that matched. The two stones were from different mines and most folk would be hard put to connect them but she commented that there were all these lights and correctly picked out the two stones that this girl had cut and also commented that she had been doing a lot of acid while cutting them. It was easily the most psychic thing I ever saw her do.


#20

First, an apology for stealing @james1’s thunder…
But I was about to mention turquoise as my 2nd favorite!

I’m not surprised, based on my own experience with recreational chemicals, and a study where different drugs were injected in a fly and fed to a spider. The web was destroyed forcing the spider to construct a new one while under the influence. Caffeine was chaotic construction while Lysergic acid produced a web that was perfect, improving on nature many times. Amazing what you can do with all eight eyeballs all focused on a target!