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 Post subject: resizing a gemstone
PostPosted: Thu Mar 12, 2015 10:30 pm 
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Joined: Tue Feb 26, 2013 11:43 pm
Posts: 25
I have to reduce the size of a gemstone and this is new stuff for me. So I assume that I will have to use a grinding stone to do that. I have a dremel drill and a bigger drill. Any tips that anyone can give. The stone is a black onyx and I have to grind off about 1/3 of the stone to make it fit.


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 Post subject: Re: resizing a gemstone
PostPosted: Thu Mar 12, 2015 10:58 pm 
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Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
That's probably not a good idea for a few reasons.
First: you don't have the right tools for cutting a cabochon, which is basically what you're going to have to do. It might be possible to do it with the dremel but it isn't going to be trivial. It'll certainly take enough time that it would make more sense to just buy a new stone.
second: many of these "black onyxes" are actually dyed agates, and the treatment often doesn't go in very deep. You'll sometimes see it on broken stones--a black skin, fading quickly through brown back to the natural color of the agate, maybe a millimeter deep. You might find that you expose an unattractive interior by doing this.

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 Post subject: Re: resizing a gemstone
PostPosted: Fri Mar 13, 2015 4:08 pm 
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Joined: Tue Jul 02, 2013 9:00 am
Posts: 1322
Location: Wylie Texas but in Alaska for a while
Recommendation:
Find a local rock club. Many have shops that have the correct equipment.
You will have two choices at most clubs:
1) Join the club and maybe take a qualifying class to get access to the equipment.
2) drop in at a meeting or a shop night, and see if someone is willing to do it for you.... if you pay them.... remember they have to pay a fee t0 use the shop equipment.

3) If you try to do it yourself:
If you do this.... which is what you asked how to do.....
1) GET SAFETY GLASSES
2) GET GLOVES (it will be sharp, especially if it shatters or chips)
3) plan on getting diamond bits. They are cheap at HB..... but you will need several and HB only has the rough ones.... You are looking for Lapidary Equipment.... or... looking for CABBING. This is probably what you are doing. (as opposed to Faceting....)

4) after it is a little bit of a mess, but before it is too small to fix.....

5) go to the club. and see if someone can fix it.

It may look simple.... and with the right tools it is pretty simple..... after some practice.

The dermal and a bigger drill....... are not the right tools.

MANY PEOPLE DO CARVE WITH THEM... not saying that..... but that is much different than reducing something by 1/3.

The cabbing machines have diamond wheels about 6-10 inches in diameter. This makes it much easer to get a smooth surface.

and you need about 6 to get you from rough cut (220 grit...) to final pre polish (14,000 grit) before you take it to the polishing machine.

Trying to do that with a typical dermal tool.... 1/2 inch in dia,,,,, really tough. Can be done.... but ther are much easier ways....

so.... go to harbor freight, pick up some safety glasses, gloves and a diamond set for the dermal.....

play

then find the rock club.

:D

You may find that you really like it, and you will certainly meet some good folks.

If you happen to be in Dallas, drop me a PM.... I can probably work something out with you.....


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