Engraving opal

For the really uninitiated, “lapidary” is a term I just googled. My very young, very not-dead geology teacher is rolling in her grave.

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Yes
I am familiar with that study. It made quite a sensation at the time.

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Particularly when all eight are on the same human woman! Lysergic Acid can make it appear that is the case also.

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Seeing as how I work every day with the fellow who cuts and polishes his own raw lots from Coober Pedy I know just how much you guys need to share about the details and how much you love the whole process :wink: So I’m not surprised at all the thread has widened to cover so much more info about the stones!

Wetting the stone did indeed reduce the contrast of the engraved lines, but they returned to normal as soon as it dried. As of this morning, the day after, there is no surface crazing or other damage surrounding the etching and the etching remains fairly well defined. No changes to it from yesterday but I will keep playing with the stone and will post magnified pictures if it does anything interesting over the next few weeks.

Yes, I’m not entirely sure anyone would choose to really do this, but you might have a stone with a lovely bit of fire in the center and a lot of mostly uninteresting matrix surrounding it. You could do something artistic surrounding the fire and have a larger stone to mount than if you polished down to just the most lovely part. So I can imagine ways to actually do something like this that would not be bad. This was just an experiment not yet an artistic choice :wink: If I decided I wanted to do something else with this stone, polishing off the etching would be very easy and not make the stone appreciably thinner. I don’t know for sure that it hasn’t made some discolorations below it, that is possible, but it doesn’t appear so upon examination. Again though, each stone and each type of stone will behave differently. This was just to prove that the stone wouldn’t just explode if you placed it in the machine.

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Never knew any of that stuff about opal… Now I’m wondering if anyone has tried stabilizing it with epoxy resin. I mean I’m certain it’d ruin the value of the gem itself, but how would it effect the overall look?

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If it were from anywhere else but Australia you would be lucky to have it at all. However, a bit of glue with some lamp black rubbed off as much as you can before it sets would bring out the engrave pretty permanently. I have seen stones with a big dead space in the center that I might risk a fancy engrave as like the termite opal anything might be an improvement and worth the risk.

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They do that sort of. By taking a very thin slice of a half mm or so and put clear quartz above and usually some dead opal below the result is called a triplet opal and can be very fiery and pretty but of course, sells for a lot less. However, if you are going to put it in a ring it would be better as your hands go through a lot that is not good for regular opals and the natural body oils that can improve an opal pendant are not there for the ring. so I have used them a lot for rings. The quartz is also much stronger against hitting and scratching as well.

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@rbtdanforth you had mentioned the horse you carved earlier in the thread about how it lived in a water jar to keep it from drying out and becoming a flaky mess, but it had been repaired by CA glue in the past. That is what prompted my musing since I’ve seen people stabilize such things as bread or piles of sand. Seems like it would be a similar process, your carved horse would still be a horse, just held together with epoxy resin and able to live outside of its watery prison.

Again I have no doubt that it would completely ruin the value, just wondering if it might be a way to salvage/reinforce those pieces that are too fragile to use otherwise while preserving the look.

Which maybe I’m weird, but if a thing looks cool enough, I’m not exactly concerned about the value.

Edit the 1st: My current understanding, baised on a quick dunk into the information super highway that is google and a read through here, is that Opal is just really pretty sandstone. Thus, in theory, epoxy stabilization should work and I’m fairly certain I’ll never be able to try due to cost/availability of opal to myself.

Sorry about derailing the thread further. I mean you could stabilize your opal before lasering it?

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Yes, the stone is pretty impervious to large molecules and even the oil may take months to soak in enough to do any permanent good. you would have to soak the horse for months in the thin epoxy starter and then apply the kicker material after drying the outside, in which case oil would be little different.

Thinking about it with what I know now I think that when the opal is formed in water and never drys out that combination of opal and water is a tiny bit bigger with the opal than without it, and since the water moves verrrry slowly through the pores in the stone it would dry out first on the outside setting up stressed that could cause the cracking or crazing. the case of the horse was so extreme that a difference in humidity from one side of the horse to another would cause it to crack.

The Honduran Opal is found in very wet environments or under water while Australian opal is found in the deserts and thus all the water is gone. If the opal is growing from the outside it would be like safety glass actually resisting fracture as opposed to the outer points shrinking that would cause cracks and crazing.

This is just my ideas having had experience with glass and the tiny amounts of different shrinking or expansion that can cause the glass to shrink or explode. There are also what are called Phase changes where the change in volume is sudden but if cooled quickly can be reheated to that point without the various phase changes that leads to that.

Zirconia clays have several extreme phase changes as they are heated and will spall (pieces flying off) if not heated very slowly, however, the final phase is called Cubic and if cooled then can take amazing heat differences and not crack even up to the Cubic phase and if cooled slowly from that runs the phase changes backwards. There is huge science in these things and I am very much an amateur but a lot of the new technical materials take advantage of that stuff.

So anyway the reason that opal cracks is just an opinion that I have not even read about.

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I was born in South Australia (the state where Cooper Pedy is located) and visited there in the late-80s.
Even then you could find poor quality opals just lying by the side of the road but it is HOT there… like ‘fry an egg on a rock’ hot.

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Sounds like a good place for a July vacation if you were looking to engrave on opal as the fire would not be a major factor in the look.

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It wasn’t until i started travel that i saw what the quality difference was between the Coober Pedy opals and the majority of other places. I have used this to my benefit though as i am quite particular when buying my wife opal jewelry and have managed some decent finds.

However now days i assume that the lesser opals are used in cheaper doublets and triplets.

Summer here in Oz, why not go now?

CooberWeather

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I presumed that July would be the coldest in OZ

Right you are… it gets down to a positively chilly 18C there then!

It is in an area that we call “past the black stump” i.e. way way out past civilisation.
I expect that like parts of Arizona and New Mexico (for example) it is a place you want to see at least once in your life… but not live there!

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I was delivering newspapers in Tucson in weather that was 15 degrees but that was F and not C. As there is no humidity to moderate temperatures there are very wide swings down as well as up. There are even rare snows in the valleys and almost every year in the mountains as much as 9 feet one year in one snowfall in that case killing a troop of boy scouts that had not expected even cold weather. That year there was 6" of snow in the valley even and it was mid November on my sister’s birthday and the most I remember.

However even in Death Valley it would drop below freezing some mornings due to the latitudes. That is California and much hotter than New Mexico that is mostly high country but even in the southern parts (that I have been through) it is sagebrush on sand dunes and really boring drive till dropping down into Las Cruces that is near a thousand feet lower than the desert above and a tough drive that many overheat on the way up.

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We have almost the exact same forecast except our temps are F and it’s not showers we’re getting but 5" of snow :slight_smile:

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Man I LOVE this forum !!!

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^^^^^^
What do you expect ? We’re family !
:upside_down_face:

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Out to the west of Tucson it gets pretty bleak and much smaller mountain and lots of sagebrush flats Where the Gila River runs into the Colorado River or would if it ever made it before sinking out of sight, as now the Colorado no longer makes it to the ocean much to the disappointment of many species that only breed in the once brackish waters of its delta.

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Hey, tangential question for you opal experts (aficionados?):

Do you think that boulder opal would be easier or harder to laser engrave than fire opal? I recently came across some at a very good price, but held off BC I was concerned that the matrix/mixed composition might be problematic to laser. Thoughts?