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 Post subject: Re: Carbonado diamond coating?
PostPosted: Mon Mar 18, 2013 8:23 pm 
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Barbra Voltaire wrote:
There is no interest in this material gemologically, aREa 541.

We are all familiar with the material from a mineralogical perspective.

Carbonado is a massive, opaque, gray, brown, or black variety of diamond used as an abrasive and in rock drills. It is not a gem.

If you feel this curiosity is worth the prices you were quoted you should buy it. If you think you can hype it up enough to sell it, carry on.

But don't think for a second that our lack of enthusiasm is the result of a lack of expertise with the material. I think it is because we thoroughly understand what it is....and what it isn't. :D


I didn't mean to offend anyone with that statement, I realize you are professionals in your field. I only assumed that there was little expertise on carbonado because my posts have been followed with questions and not answers. I am sorry to assume, and I apologize.

I am just confused by the conflicting statements from an expert here in relation to a report from GIA. I also never got any answers to my original question which was about the coating. Could somebody confirm that carbonado cannot be faceted, and explain how GIA could be mistaken with their identification?


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Mon Mar 18, 2013 8:58 pm 
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As we can see in the article quoted:
Image
I don't think the GIA made an error in ID.
As far as the coating, as you suspected only the seller knows the specifics on that.
Let us know if they ever get back to you.


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Mon Mar 18, 2013 9:12 pm 
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Thanks Barbara, I will.

I am going through a different supplier than the first one in India who had the coating listed on the data sheet. I am highly suspicious that supplier was just supplying treated black diamond, not actual carbonado. Especially since India is the largest supplier of treated black diamond due to low labor costs and the amount of time it takes to facet black diamond.

The supplier I am going to use now doesn't coat their carbonado, but says if I want it they can do it, (though he said it is a process used for treated black diamonds). This supplier is located in Belgium. The price list I submitted was from this supplier. He seems to be very knowledgeable about this material and like the most trustworthy supplier I have talked to. Has anyone here ever bought this stuff in gem form? Are his prices where they should be, or are is there such a limited market, there isn't much of an established pricing for it?

Thanks for bolstering the GIA report Barbara, all I am looking to do is make sure I am getting the right material. Any naysayers feel free to chime in on why it might be wrong.


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Tue Mar 19, 2013 3:24 am 
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While carbonado can not be faceted there is modern laser technology available for polishing even nano-polycrystalline diamond. It is based on precise stepper table and short localized laser pulses. Even perfect round is possible. Good example of this is nano-polycrystalline diamond ball described in Gems & Gemology Summer 2012.

Coating for carbonado? I have to say it sounds really weird.

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 Post subject: Re: Carbonado diamond coating?
PostPosted: Tue Mar 19, 2013 6:33 am 
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Carbonado & Bort both are polycrystalline thus they both have industrial use not jewelry but collectable curiosity is always exception. one can also be interested in rocks from moon or mars :D . i remember a TV show about Meteorites collectors they pay crazy money for these stuff!
i am also interested to add a nice color (brownish or greenish) carbonado to my collection
Formation of Carbonado is not clear, main hypotheses include metamorphism of earliest subducted lithosphere, radioactive transformation of mantle hydrocarbon, meteorite impact on concentrated biomass, or extraterrestrial materials.

faceting Carbonado is very difficult and hard job, it might take months of faceting and sometimes you can not facet some direction at all!
i have never heard of coated Carbonado, maybe its sintered diamonds they are selling you?! remember sintered diamond is not natural.

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 Post subject: Re: Carbonado diamond coating?
PostPosted: Tue Mar 19, 2013 4:29 pm 
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aREa 541 wrote:
AlBalmer wrote:
aREa 541 wrote:
I am drawn to rough specimens more than cut and polished gems.

Then, why do you want faceted specimens? Aren't specimen rocks generally more valuable "as found", or even in matrix?

I will be setting these in jewelry, as much as I like raw specimens, I don't think they would look good for what I am trying to do.
thomas.adamas wrote:
Barbra Voltaire wrote:
I was finally able to load the pdf.
Question: Does carbonado have any real "value"? Or is it just a collectable curiosity?

I have experience with both carbonado and black diamond.
Carbonado is a random oriented polycrystalline form of diamond, thus cannot be faceted on a scaife. Real diamond of black color is polycrystalline with a preferred orientation, so while it runs slowly, one can facet it on a scaife.
If a diamond is faceted, it is NOT carbonado. If such a stone were diamond, it is just black diamond.


So are you saying that the GIA report misidentified the carbonado because it is faceted? If you look at the surface of the stone, it is much different from any black diamond I have seen, and looks like the "carbonado" that I have been shown. I am not trying to doubt you for no reason, it is just that a GIA article carries a decent amount of weight.

Yes, those stones do look like carbonado. I wonder if those were cut with a laser to make facets. I see no point in doing so other than to show what a laser can do.

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 Post subject: Re: Carbonado diamond coating?
PostPosted: Tue Mar 19, 2013 5:35 pm 
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I agree Thomas. I think the GIA got it right AND that these were fashioned with laser assist.

I think it might me confusing when we say that the material can not be faceted when clearly the GIA posts pics of fashioned carbonado. Laser fashioning is not the same as faceting. I'm sure you can explain this better than I Thomas and Mikko.


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Wed Mar 20, 2013 6:41 am 
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The technical term used for laser fashioning is "laser ablation" and that method is likely how surfaces were cut on the carbonados. I did not know that GIA color grades opaque diamonds.

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Last edited by thomas.adamas on Wed Mar 20, 2013 8:46 pm, edited 1 time in total.

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 Post subject: Re: Carbonado diamond coating?
PostPosted: Wed Mar 20, 2013 6:31 pm 
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Ablation?

The only thing I could find on laser ablation in relation to gems seems to reference a way to examine their chemical makeup. Could you expand on it a little more so I could get an idea of how it works?

I definitely believe that lasers have the power to do such tasks, as I have done research in the past on them for my glass business. Just trying to get to the bottom of this whole carbonado thing, I feel like I already have a much firmer grasp thanks to you guys here and some other experts I have been talking to.


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Wed Mar 20, 2013 10:28 pm 
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I found this page on Wiki:
http://en.wikipedia.org/wiki/Laser_cutting


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Mon Apr 01, 2013 3:37 pm 
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Hi,

A few years ago I had to examin a carbonado of over 2000 cts. One cannot polish any facets on it. The only way is facetting by laser, and then try to smooth it on a disk, but I have serious doubts if one can smooth it. I had a small part removed by laser, and asked a friend, he has a diamond polishing plant, to polish the facet. After some 20 minutes he came back explaining that he would be destroying his disk if continuing, and when he gave the stone back to me, I could not see anything polished on it.
I met the owner again, a few month ago, he wants to polish the stone, but no one would do it, and nobody knows how, not even comdiam.
That's what I can tell you about carbonado.

Regards,


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Mon Apr 01, 2013 5:26 pm 
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Thank you, that is some very relevant real world info there!

Did you look at the link I provided with faceted carbonado from GIA? Is that the finish that can be acheived with laser (does it look similiar to what you saw after laser cutting), or do you think those were somehow polished beyond the laser cut?


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Thu Apr 18, 2013 7:30 pm 
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Quote:
Upon further inspection of his data sheet, it says they are "coated"


Black DLC coating maybe?


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 Post subject: Re: Carbonado diamond coating?
PostPosted: Mon May 06, 2013 10:49 am 
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Here is more info about laser polishing: http://www.gia.edu/gems-gemology/SP13-LN-buff-top

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