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 Post subject: Moissanite !!
PostPosted: Tue Dec 30, 2008 9:02 pm 
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A quick question for my fellow Faceters ! Has anyone cut Moissanite or is it even possible with our faceting equipment at a Mohs hardness of 9.5 ?
I'll do another general search but wanted to post here first.I've never really considered cutting man made before and have a couple of customers who are interested. I quite honestly had never heard of it. Some sites are plugging it as not harder but tougher than diamond great dispersion and RI.

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 Post subject:
PostPosted: Tue Dec 30, 2008 9:31 pm 
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Quote:
A quick question for my fellow Faceters ! Has anyone cut Moissanite or is it even possible with our faceting equipment at a Mohs hardness of 9.5 ?


Yes, it is possible. Several years ago I got a frantic email out of the blue, from a diamond cutter who had to repair one. He was dying with it.

We discussed things back and forth, and what equipment he had. I suggested copper with a LIGHT charge of diamond. The next day I got a very grateful email from him, so it worked.

Moh 9.5 is still miles away from diamond, since the scale is not linear.

I look forward to trying one someday when the rough market loosens up.

Given the size and global nature of this forum we will probably be hearing from someone who cuts it.


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 Post subject:
PostPosted: Tue Dec 30, 2008 11:19 pm 
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Hi Gearloose! Thanks for the quick reply,I knew one of the regulars would be around. Yes It seems virtually impossible to source rough material,a company named Colvard something or other seems to have the manufacturing patent. What I could find online might as well be diamond for the price! Looks like fairly interesting material though. Something noble about such a hard man made material!
Thanks for the cutting info though,I learned something!

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 Post subject:
PostPosted: Wed Dec 31, 2008 12:56 am 
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selous,

Charles and Colvard (sp?) do cut and sell moissanite. The actual material is made by Cree, better known for LEDs.

C&C keeps careful control of all the Moissanite rough they get (all that Cree makes) and will not let ANY out of their control, outside of rough they ship to faceters who cut it for them. Yes, it does cut on standard faceting machines, not diamond faceting machines.

I had thought that a piece of opaque moissanite would make a good lap tool, in the same way that a Norbide stick does, except that the moissanite can be a bit harder. But C&C was not interested at all.

There was a bit of a cutting quality problem a couple years ago, and multiple professional faceters recut some stones for folks who had bought it. Go to the USFG Yahoo group and look up moissanite for what they said. There used to be a C&C person who belonged to most faceting groups and monitored them for any mention of moissanite. Given the current economic conditions, I don't know if they still do that, or if they are members here.

There is at least one other company that has learned to make transparent silicon carbide (I think that's what moissanite is) but whatever it is, at least one US university has made some in the lab and somebody in Europe, maybe Russia, was reported to be able to make it as well.

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 Post subject:
PostPosted: Wed Dec 31, 2008 3:31 am 
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Hello Selous,

Yup Moissanite is CCC's trade name for silicon carbide the well known Union Carbide grinding wheel stuff. It cuts and polishes easier than sapphire but you are going to have a problem getting any rough unless you want small stones that are blues, greens and yellows.

Back in the '70's I had a rock shop and we had a case of 'synthetic' mineral specimens, a couple of the larger SiC crystal sprays had shed some of the larger tabular crystals and I cut a few, the blues were very striking but I got nothing over 3 1/2 mm. You should be able to track down a crystal spray but there won't be any white ones

I did get quite a few damaged SiC's from our local diamond cutter but now they come direct. Recently however I received one for repair and upon quoting my regular repair price the customer turned it down telling me it would be cheaper to just replace it. The 1 1/2 ct princess cost them less than $50 for the stone. They were purchased in China.

Why would anyone want such an ugly brown stone anyway?

Tony.
a recent recut;
Image

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 Post subject:
PostPosted: Wed Dec 31, 2008 8:16 am 
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Charles and Colvard (sp?) do cut and sell moissanite. The actual material is made by Cree, better known for LEDs.


Ah, that's the connection. Cree was the first to make a blue LED, and SiC was used as the semiconductor.
It was a breakthrough because a blue LED was a sought-after item for those huge outdoor display. We had red and green LED's for years, but the displays were not possible till a blue LED was developed. Hold a loupe up close to your monitor and see why everyone was desperate for the blue LED, remembering that we already had the red and green.


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 Post subject:
PostPosted: Wed Dec 31, 2008 10:31 am 
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Thanks for all the info guys! I'm not going to pursue this any further because the only material I've been able to come across rough is the forementioned tiny pieces manufactured in Russia and weighing in at a whopping .5 - .89 cts and a price tag of $5 - $15/ct.
Quote:
Yup Moissanite is CCC's trade name for silicon carbide the well known Union Carbide grinding wheel stuff. It cuts and polishes easier than sapphire but you are going to have a problem getting any rough unless you want small stones that are blues, greens and yellows.

Maybe this material will be worthwhile looking at once it becomes easier to source decent rough material. Untill then I wouldn't waste my time. Interesting discussion though!. I have definitely learned something as I had no clue this stuff even existed untill starting this thread yesterday.

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 Post subject:
PostPosted: Sun Jan 04, 2009 2:40 pm 
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Thanks for all the info guys! I'm not going to pursue this any further because the only material I've been able to come across rough is the forementioned tiny pieces manufactured in Russia and weighing in at a whopping .5 - .89 cts and a price tag of $5 - $15/ct.


Give them a year or two and watch. The Russians are among the best, if not the best, crystal growers in the World, and have been for decades.

If they smell money, they'll be selling stuff big enough to use as boat anchors before long, like they are doing now with citrine.

In the 80's I used to get a lavishly-illustrated magazine, SOVEXPORT.
If you needed a sapphire crystal shaped like a corkscrew with the C axis centered in the helical rod, they could do it.
We used to buy Bridgeman Bismuth Telluride from them. Cheap. (Well, at first..haha.)


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 Post subject: Re: Moissanite !!
PostPosted: Mon May 07, 2012 4:45 pm 
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Is there anyway to get rough Moissanite now? I know it was hard to get in the past but I wonder if it is still almost impossible to get?

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 Post subject: Re: Moissanite !!
PostPosted: Mon May 07, 2012 6:31 pm 
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It's around now, but not water-white. Slight tannish, grey tint. I have a small piece and intend to cut it when I get the time. I would expect much of the tint will be "Lost in the glitter", but there's no way a "Color A" stone is going to result from this piece.


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 Post subject: Re: Moissanite !!
PostPosted: Tue May 08, 2012 2:48 pm 
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I am not seeing any around that are good white colors as well, or even cool colored material. Hopefully they will start to show up more.

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 Post subject: Re: Moissanite !!
PostPosted: Mon Apr 22, 2013 10:20 pm 
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Sorry to bring up the old post, but does anyone have a moissanite rough that can be cut into around 6.5mm OMC or OEC? I'm actually aiming to get the champagne color that everyone else scorns. :roll:


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 Post subject: Re: Moissanite !!
PostPosted: Tue Apr 23, 2013 1:07 pm 
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I have done a number of re-cuts on moissanite for clients and all of the moissanite which I have re-cut in the last couple of years, (maybe a dozen), have turned some shade of brown. This ranges from a strong tea color to a light overtone of that same color. The lightest changes have been with the new, treated materials which, I believe, are hot isostatic pressed to reduce internal micro-defects and so decrease the apparent color of the material.

From your point of view it will be very difficult to estimate the final color if you're doing a re-cut. If you aren't too concerned, then you could just buy one of the untreated moissanites in a slightly larger size and do the re-cut to your preferred design. If you haven't re-cut this stuff you should be warned that the original cutters often cut it very shallow and so your design may not fit for depth, (requiring you to modify your design or cut it smaller.

Here are some that may work for your needs: http://tinyurl.com/cevtsgd

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 Post subject: Re: Moissanite !!
PostPosted: Tue Apr 23, 2013 2:54 pm 
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I have experience with Moissanite: Several times a jeweler had given it to me as a diamond, and also as Moissanite.
On a diamond cutting scaife, facets lap very quickly, so that is a dead giveaway that the material is much softer than diamond. Moissanite wears plated diamond laps out very quickly. If you use sintered diamond laps, you need to dress the surface often. While Moissanite is considerably harder than sapphire or ruby, it is more brittle, so no polishing on a ceramic lap as the facet meets will chip and cause scratching. I would recommend polishing with diamond on a BA5T or a Matrix lap.
I prefer the appearance, cutting and polishing characteristics of CZ over Moissanite.

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 Post subject: Re: Moissanite !!
PostPosted: Wed Apr 24, 2013 12:55 am 
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I saw the pictures of the recut you did (michael e) on the other forum. My first impression was that those stones are more brown/champagne than tea green. I wouldn't really like the green cast.. maybe it was the white balance in the pictures, but I did not see any green in those recut stones.

What size RB stone would be needed to end up with a true OEC proportion (if there's such a thing) of 6.5mm diameter with high crown and such?

Also, how would you compare the colors of the recut moissanite stones to champagne colored diamonds?


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