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Hole in onyx

A customer of mine wants a bezel set diamond solitaire pendant
surrounded by black onyx, where the bezel is actually inlaid in the
onyx. She wants about a .75 ct, which would make it a 6mm stone, or
about a 6.5mm O.D. bezel. What is the best way to cut a perfectly
round hole in the onyx, or is there anyone out there that would be
willing to cut the onyx for me? I estimate that I want it about 12 -
15mm in diameter and about 3mm thick.

Wendy Newman

hi wendy- I’ve done quite a few projects like this and the problem
with drilling a pre-cut cab will be orienting the hole and avoiding
chipping around the edges. I don’t know if you are set up for lapidary
but, if you are or know someone who is, the best way to proceed would
be to drill a slab of onyx with a diamond core drill keeping the
drilling area submerged by making a tinkers dam out of modeling clay
or sticky wax. Get as close as possible to your finished hole size,
unless you’re very lucky you will need to ream the hole to its final
size. Then you can cut the stone around the hole to center it, that
way you lose the chipping when you cut the top. It’s not a bad idea to
go in after the stone is cut and very slightly round and polish the
edges of the hole for a more finished look. I hope this is helpfull,
feel free to email me if my descriptuon here is too brief.

Hello Wendy: I am here in Houston, Texas. I am a graduate gemologist
and a professional gemstone cutter to the trade (facet and Lapidary).
If you can’t find someone closer than me I would be willing to do it.
My normal charge is $10.00 plus postage. Ed Katz, G.G., 6222 Richmond
Ave., Suite 555, Houston, Texas 77057.

Hello Wendy!

If your not familiar with cutting and lapidary, this onyx job is
probably a good opportunity to find a good cutter inlay shop to do it
for you. As I recall the last hole I had drilled in onyx (3 years
ago, or so) was about $10. You should be able to find a suitable
shape available without cutting from scratch. Most gem suppliers have
cutting services available.

I will make one suggestion that may make it turn out nicely. Set your
stone in your tube and bezel. Send it off, or deliver with the onyx
to the lapidary person. Tell them how deep, and where you want it. A
good cutter will fit your bezel to the stone much easier than you
could fit the bezel and tube to the finished hole. When both pieces
are returned with a nice fit, you will need to cut the tubing with a
saw, and burnish against the back of the onyx. Make sure they cut a
couple troughs on the back of the stone to firm up the burnished

Ask around a bit, you have an opportunity to find a lapidary person
to save you time and hopefully do some nice work for you. Good luck!