Etching and cutting semiprecious and precious stones


#1

I’ve been seeing some incredible inlaid stone designs lately, made mostly with lab-grown stones such as opals. Any thoughts about stones that GF will or won’t be able to cut or etch?


Etching other stones?
Etching other stones?
#2

Don’t see how a 40W CO2 laser would be able to do that. Not even sure I would call it etch. More like a marking of stone. Or a miniscule shattering of the very top layer.


#3

It will not cut them at all.

They have said it can etch surprisingly well on materials they were not sure about. So hope for the best there.


#4

Engravers will usually mask stone that is not directly engravable or harder to work with then sandblast the exposed. I have done this with many non precious stones. My concern with opal, is it not a soft stone? I would be worried with it cracking etc. You could always try a google search to see if anyone has had direct experience trying this. The closest I have done is possibly a geode. Let us know what you find out. Cheers.


#5

Opal is a pretty soft stone which is very sensitive to heat and dehydration, plus has a high variation in index of refraction (ie: won’t cut well) due to it’s microstructure (the beads within the bulk opal). I would never even try opal in a laser engraver/cutter.


#6

@morganstanfield, interesting idea.
Regarding opal, as a lapidary it is a favorite of mine and I have cut a few pounds. Hydrated (containing water in chemical association) form of silica.
Since it is amorphous ( non crystalline) it is a softer stone, 5-6 on the Mohs scale.
The water content is the problem. Anywhere from 6% to 20%, and the concentrated heat from a laser would qualify as a thermal shock.
I can’t say definitively because I never tried it, but flashing the moisture content to steam would likely be the end of the stone.
Try it on a scrap first, but I wouldn’t be brave enough to try a finished cut of precious opal.

Mineral engraving sounds intriguing, but from my work in cutting them, I know there are inherent hazards posed by specific minerals, which is why they are cut on a wet grinder.
Anything cupric (copper) like malachite, azurite and turquoise will produce fumes to be avoided.
Lapis can have a high sulphur content. Even on a wet grinder lapis leaves the taste of a struck match in your mouth.

I’m sure I will have to experiment with minerals at some point, but I won’t have the courage to feed an opal to my laser… Unless I’m OK with it going away.


#7

I have seen it mentioned somewhere on these forums many months ago that laser etching or cutting doesn’t really heat up the object as a whole, because it focuses its energy on each tiny (~0.01mm) spot for only a small fraction of a second before it moves on to the next spot. On the assumption that a laser could in fact cause material to be removed, the very small steam flash from each spot may actually be more likely to just help to eject the ablated material from the kerf than to destroy the stone. However, if the water content is highly variable throughout a single stone, you would likely see some variation in the amount of material removed from each spot, which could in turn produce rougher edges.


#8

Since silver soldering near opal is already a problem (yes, I made that mistake once), I suspect the laser would cause serious damage in most opal.

Less hydrous minerals should have fewer problems - but be careful about the chemical content and physical structure: you don’t want to breathe serpentine dust, because it’s pretty much asbestos. And you don’t want to breathe in a lot of lead, arsenic, copper, or other heavy metals (or even get many of them on your skin in powder form).