I was just setting a moonstone cab and stupidly scuffed the top with a pair
of pliers (not a cut, just a scrape that looks like it was sandpapered). I
don’t have any lapidary equipment, so can anyone recommend another way of
trying to buff it out?
Many thanks in advance,
Assuming that you have a flexshaft motor and handset, go to the website of Kingsley North and see if there might be an inexpensive flex shaft based solution. Otherwise, look for the closest Gem and Mineral or Rock club as there will be someone there who can help. Since the damage is on the top of the stone, you should be able to polish it out without removing the stone. I polish some softer stones with Zam while in the setting. I can’ guarantee that this will work for moonstone. Others on Orchid may know. Good luck…Rob
Here’s what I do for minor scuffing on stones that are comparatively soft -
eg opal, moonstone, labradorite. Glue some 1200 grit wet or dry paper onto
a popsicle stick, gently go over the scuffed surface (usually I do this
wet) until you’ve sanded all the marks away. If the scratches are deep
start with 600 or 800 grit. Be careful - fresh 600 grit will cut fast on a
moonstone. Once the surface is at a uniform smooth 1200 finish then polish
(again wet) with cerium oxide on a felt or leather wheel held in the
flexshaft. Moonstone being a feldspar you’d probably be better off using
diamond instead of cerium oxide; 8000 diamond grit gives a very acceptable
commercial polish. Again as carrier use a hard-ish felt or leather wheel
held in the flexshaft. Diamond grit comes in syringe-type dispensers and
is grease based, so you won’t need water. Go gently, check progress
frequently. The grease carrier will tend to hide scratches, so wipe the
stone off with alcohol or other solvent to see your results.
Sara, there is a learning curve to
doing lapidary work. If you can, break it
out after you find a replacement, you could
spend money and hours and not be happy
with the results.
It is a skill achieve through practice, and
time better spent learning to not scratch
That gets expensive, regrettably, my
Thanks all for your suggestions. I’ve certainly learned my lesson and will
be taking the flex shaft route to try and fix it.
I find ZAM on a stitched cotton buff or the felt tips works rather well on stone scuffs.
I second using zam.
I use these (somewhat expensive) porcelain type abrasive wheels for high polishing graver faces. But they also will remove and polish abrasions from fairly hard stones, like a garnet. It’s a hard wheel so you can almost maintain the facets. They are really useful wheels and last a long time if you’re careful.
Here is another wheel that I have, I’ve only used it once. It’s softer and squishier and it’s sort of ‘juicy’ when you use it. But it does a nice job on a cab.
Yes, you can use your flexshaft and polishing wheels for this, but it is even possible to do it with a couple of pieces of emery paper, maybe a 600 grit and a 1200 grit or 3000 grit or something close to these. A little water as lube on a piece of wet-or-dry paper. Set the paper on something soft, such as a mouse pad and move the set stone around until the scratches are gone. You can press as hard as you need to to make the emery paper conform to the stone’s curves. If the scratch is only on top, just press lightly to just work that area. For stones below Mohs 8 in hardness, oxide polishes such as cerium are more effective in polishing than diamond. Cerium is pretty cheap and you only need cab grade polish. You might even try going to a local optician to see if they would give you a little to use. You can try ZAM or rouge, but I’m not sure they would work. Linde A would work, if you had some. Diamond may leave you with a hazy polish, not sure as this isn’t recommended for feldspar, so I’ve never tried it. Just get a piece of felt or even pellon or cotton and apply the polish and a little water and rub briskly. A polish should come up quickly if the scratches are all sanded out first. If scratches remain, go back to the sanding steps. Lapidary polishing on cabs is not rocket science and should be pretty easy. It is trying to eliminate scratches on the tables of faceted stones with a flexshaft where jewelers get in trouble.
If you don’t want to fool with this, get in touch with the local gem and mineral club, as there are many lapidaries who could take care of this in 5 minutes and maybe they would like to meet a jeweler who could provide mounts for their stones. You might also find a source for stones for your work at a good price.
Thanks all! Excited to remedy my blunder.
Sarah, Rob, Hans & Richard,
In Rio’s Tools catalog, on page 436, "A"is Sapphire powder, “B” cerium oxide .
With a medium or hard felt buff would these abrasives work ?
Polishing involves using a method
of sanding course enough to remove
the deepest scratches, then finer and
finer until it is time to polish.
Usually the progression is something
like 220, 400, 600, 1,200, 3,000.
You might be able to use 600 and then
cerium oxide on a hard felt wheel with