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How to split/divide a nephrite jade cabochon in two?

Hi!

I have a customer who would like me to split a nephrite jade cabochon in two (the parts doesn’t have to be of equal size or be “perfect”). With jade being so tough, would that even be possible without specialist equipment? I have no lapidary skills. Also, the nephrite sits in a heirloom gold ring so it is very much irreplacable.

Thanks!
-Silje

I don’t know which way you want to split this…like making an 8x10 into two 4x10s or slitting it into two thinner pieces…the former being a bit easier than the latter. While you could probably accomplish this with some diamond slitting blades in a foredom, lubricated with oil or water, the easiest way would be to find a lapidary with a faceter’s trim saw or small, thin bladed lapidary saw. If you’re slitting into two pieces that are under 4mm in thickness, it is possible you will break the cab, altho’ jade, being both tough and hard, stands a chance of coming out into two pieces. If slitting, you might have to bed the piece into plaster so it could be held, but maybe hand holding would work…it’s something the lapidary would have to see. To the extent that cabs have patterns and the customer wants the original back, yes, it’s irreplaceable, but generically nephrite, even really good nephrite, is readily available and could be replaced.
People come to us all the time expecting the impossible. Any time you start to cut a gem, you should make sure the customer knows the risks and assume no liability for breakage. All the gem cutters I know of, when undertaking to fix scratches and chips in faceted stones, have a waiver of liability that the customer has to sign. You can tell people what the likelihood you’ll break something is, but you can never rule out the possibility of an accident or a flaw in the rock that wasn’t apparent. A straight thru cut into two half size cabs isn’t very risky, but a slitting job is somewhat so. Unless I had expertise in this area, I would refer the customer on to someone else who did and no matter what I did I would have that waiver. I would also use my judgement of how reasonable the customer seemed to be…good luck! -royjohn

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Thanks for good advice! The cab is quite large, but it is irreplacable in the sense that it belonged to a deceased mother and the daughters now want to split it and have one piece each set in a new piece of jewellery, so it has to be this exact nephrite. I had a strong feeling that I should not do it, so thanks for making me more sure not to do this myself! :slight_smile:

-Silje

If you take a 30x40 or so and split it into two 20x30’s, that’s not very risky, but I’d still farm it out to a lapidary and then it’s on him to get a waiver. Nice idea, tho’…could even cut it on a slant and then the girls could pick another cab and cut it similar and have an oval with a gold or silver line down the slant division in the middle…kind of an old + new symbolism… some people just love such stuff…

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If you haven’t already found a lapidary, a search for “rock and gem Club” in your area would be a good place to start. Any club would have some experienced cutters. Ask for someone with jade experience. Getting a good polish on jade requires both knowledge and experience.

Adding to royjohn’s good advice. Regardless of how you split the cab, there will be some grinding, sanding and polishing needed, especially if the pieces will be set into new jewelry. This takes specific lapidary equipment and skill. You need to find someone with this equipment and skill or learn it yourself. Start with your local gem and mineral or rock club. Good luck…Rob

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I live in Norway (very few people, great distances - things are different here). But thanks anyway!

Since this is a wide ranging site, it is sometimes hard to put a post into geographic context. If I weren’t a lapidary, I to would be hard pressed to find someone to do what I and others have suggested that you do. You might consider asking your customers if they would be happy with the jade just simply being cut in half. You would have the original finished edges to work with and the exposed unfinished edges might then be thought of as having some kind of symbolic significance for the sisters. I have made a number of pendants this way with polished surfaces adjacent to natural unfinished surfaces. As long as you can secure the two pieces of jade in a setting, it would all work. As for getting it cut, jade or nephrite is hard and it tends to split unevenly when you get to the end of the cut unless you go very slowly. There may be small narrow tile saws that can cut it, but I would still look for a lapidary with a narrow trim saw. Once cut the edges will be very sharp and you will have to find a way to dull them a bit. You can do this with various flex shaft mounted tools. Please keep us posted on how you solve this problem and good luck…Rob

The customer just wants the nephrite to be in two pieces instead of one - it doesn’t have to be a neat parting with nice edges. Uneven splitting is no problem! As long as two pieces survive, the problem is solved. If 50 % of the stone is broken and can’t be used, that’s ok too, as long as there are two pieces left, regardless of size/shape. The piece of jewellery and mount will be made to fit the fragments, so I’m not really concerned about sharp or uneven edges: I’ll just hide the less fortunate parts of the stone. Maybe I should give it a go, then? Thanks!

You might treat it like glass. Cut a score line down the middle with whatever you have and then try to carefully snap it along the score line. you could use a thin separating disc on your flex shaft to score the line if you have one. Good luck…Rob

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Here are some organizations that might be able to provide some assistance:

Norske Amatørgeologers sammenslutning (NAGS)
Follo Geologiforening
Fredrikstad og Omegn Geologiforening
Harstad Geologiforening
Østfold Geologiforening
Stavanger Geologiforening Norske Amatørgeologers sammenslutning (NAGS)
Follo Geologiforening
Fredrikstad og Omegn Geologiforening
Harstad Geologiforening
Østfold Geologiforening
Stavanger Geologiforening

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Have you ever tried this “glass” method on nephrite? I doubt it would work very well. Nephrite is not particularly hard, but it’s very tough, being composed largely of fibrous minerals (tremolite and actinolite) that interpenetrate each other much like the fiber mats in composites like fiberglass. That’s why neolithic people prized it for use in tools; it’s highly resistant to breakage. I’d advise finding someone with a diamond trim saw, as was previously suggested, and using it wet to avoid sending respirable particles into the air.

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Never tried it, just trying to help the OP figure out how to break a piece of nephrite without the use of a saw. They apparently don’t care what kind of edge is left or how many pieces there are as long as two of them can have a piece of the original cab. A rock and hard place so to speak…Rob

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Most minerals and gemstones can be cleaved, or split. Nephrite is one of
the few that cannot. So, you should cut it on a saw, or have it cut. This
is 15 seconds on a trim saw. Otherwise, don’t take the project.

Otherwise, the overwhelming reason why you wish to screw up your
customers stone, and have them mad at you, is, what,exactly?

you can also try a diamond slitting saw, 1" / 30 mm in diameter, which can be used in a flex shaft. must be used wet. you must practice on
a trial stone, or you will screw up your customer’s stone, leading to the
same questions above.

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As long as the customer is clearly informed of the risks, and still wants me to try (even if it means the stone will be completely ruined), I can’t see why not. The cab is quite big, so I believe I can try several times if the first try proves to be a failure and still get two pieces, however small. Also, the cab is very worn, so I think the symbolism of the stone is more important than its beauty in this case. With all the good tips this post has given me, I believe my customer will be happy, and I will have tried out something new and gained some experience :slight_smile:

Why do you wish to trash their stone? I fail to understand why you are
rationalizing how the customer will be happy with your destroying
something of high sentimental value, that this is somehow acceptable. It
is not.

Your customer has asked you to “split” the stone. You should
know they are ignorant of the proper term, so they have not asked you to
literally “split” the stone. They mean, they want two smaller
stones, and are relying on your technical expertise to do that.

You can do a proper cut, and then have two stones that fit together; you
can make two pieces of jewelry for them, each that looks like it has a
sibling in the other; you will then have two customers for life.

I did use a partially split technique once on jade, for a large (640
pounds, 290 Kg) Wyoming jade boulder, which was too large to fit in my
24" saw. I built a 6 foot drag saw to make a cut most of the way
through, that cut took about 12 days; then packed the cut with dry wooden
wedges, and then soaked the wood. The expansion of the wood due to the
water was enough to split the boulder pretty much where i wanted although
it took a final pop with a 12 pound sledge to make the actual split, this
gave me two pieces, about 200 pound and 400 pounds which can then be
worked into my largest slab saw (24" saw). this is simply a modern
variation of stoneworking techniques use to quarry stone for the
pyramids. It works on a large scale as the pressure exerted by a large
amount of swelling wood (up to about 900 psi) is more than the tensile
strength of nephrite (also up to about 900 psi, hence the need for a
small hammer smack)

So, yes, it can be split, but not on the scale you are talking about, a
jewelry sized piece; you will simply get garbage. No one will b happy,
and you will not have learned anything

I do not know what part of the world you are in, but this is a simple
project, it has taken me longer to write this than it would to
actually make the saw cut; if you pay the shipping both ways, and include
proper shipping docs and packaging for the return trip. I am happy
to do it for you at no charge. (I am in Denver Colorado USA) or find a
local cutter; you will then have a connection for your next project,
speaking of trying something new

If you read all of the post in this thread you will learn where Silje lives and why this is a problem. As you suggest, making sure that the customers understand the possible results of what they are asking is important and it is the jeweler’s responsibility to cover this requirement. I enjoyed your story about splitting a large Jade bolder. It could have come from an old issue of Lapidary Journal…Rob

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I will discuss with my colleague and customer how to proceed. With good communication, I’m sure we’ll come to an agreement.

Shipping distance. Hmm. Well, one time I bought a CT Scan in Norway
(Oslo) and shipped it to a remote village in the Democratic Republic of
Congo, so perhaps I am not impressed by shipping things around.

A diamond slitting disk for a flex shaft should be available for $15 or
so (about 13 Euros), that would at least let you make the one cut, enough
to split the stone. It is simply a steel disk with diamond plating, a
small saw that fits on a arbor and used in your flex shaft.

Yes, the jade boulder approach was inspired by old Lapidary Journal
articles from the early 1960’s, basically a mud saw. The old
techniques work pretty well. That saw, no real design, just a
motor, gearbox, crank arm, and a piece of steel that we were going to use
to edge a flower bed in the garden. I use a CNC mill to machine the crank
arm though. And a bungee cord to keep tension on the blade, opposing the
force of the crank arm. The bungee was anchored to a bunch of mil
crates piled on the floor filed with, what else, cutting material. A 600
pound jade boulder gives you, well, alot of material to cut and carve,
More than you need.

Ah, sorry, off topic, I have too many stories.

Come to think of it, you could use a hand-held hack saw (reverse the
blade so you are using the smooth side with no teeth), and a slurry of
220 grit carbide, to make two slits on opposite sides of the cab, then
make a notch on the backside of the cab; support the cab at both ends on
top of two regular drill bits, then tap the front of the cab with a
hammer (put a piece of leather over the hammer face), and that should
split it, as long as you get the notches about 1/3 of the way across the
cab.

Anyway, best of luck with it Siljie.

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What about a different solution to the problem? What about buying a new, matching stone and making a duplicate gold ring and giving one sister the original gold ring and one the original stone? Then, no risks would be taken and the stone would not be broken into two less beautiful or useful stones.
Susy