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Part II- Ten New Diamonds from NC

December 9, 2014
This octahedral diamond cyrstal looks like it has been faceted. These are all growth textures on the triangular crystal faces. Also, this is my favorite picture.

This octahedral diamond cyrstal looks like it has been faceted. These are all growth textures on the triangular crystal faces. Also, this is my favorite picture.

One of the comments on the earlier blog post came from Richard Jacquot:

rick@wncrocks.com commented …In an article published with Ed Speer in Volume 1, Issue 2 of American Rockhound magazine in June, 2014, we discussed 15 diamonds that were found in Reedy Creek in Mecklenburg County. These diamonds were found by a gold prospector and sold to a reputable local mineral dealer. They were then sold to various collectors. This was around 1999. The diamonds averaged .5 carat and 1-2mm. The diamonds have been tested and there is no reason not to believe that the prospector found these, in fact, the story is very similar to this one. So what is the criteria for getting them authenticated?

To bring everyone else up to speed, Richard is publisher, editor, and in this case, also a writer for American Rockhound magazine. American Rockhound is a new addition to the world of magazines, so the distribution is not yet large, but I wish him and his co-authors much success. Goodness grows in North Carolina, and that includes the minerals.

As with any scientific question, the question finally revolves around who has the data, and what data do we (I) have in hand? I wasn’t able to get hold of a copy of the article, so I can’t speak to any of the particulars of that diamond find and sale. I don’t know any of the people involved, so I can’t really make a meaningful comment on that, either. I don’t have any evidence one way or the other. I do know about this diamond find, so I’ll go with what I know. Here’s how I approach the problem.

“Authenticate” covers a lot of territory. It’s not like these are antiques. I knew with about 95% certainty that these were diamonds from the moment I opened the package. The next step was to collect data to support that identification. Diamonds are isotropic on my petrographic scope- that is, in cross polarized light, they stay dark. Second was to look at the composition: EDS. With the great big carbon peak, there wasn’t much doubt.

The next question was natural vs. synthetic. For that I needed the assistance of a genuine diamond expert, and Diamonds Direct Crabtree came to the rescue.  The verdict from the Gemological Institute of America was that the diamonds are natural.

The final step is like any other scientific study: reproduction of results. Could we reproduce Jeff’s findings, and then find the source of the diamonds? We were still working at that when Jeff died.

Rockhounds in the field tend to be very focused on what they want. I’m not a rockhound, I’m a research scientist. Rockhounds and other amateur geologists tend to be surprised at what I want, which is everything. A prospector may find gold in quartz veins, but then he’s surprised that I want the quartz, and the sulfide minerals. These minerals contain oxygen, hydrogen and sulfur isotopes that illuminate the origins of the gold-bearing fluid. Size is not an issue for analysis. The quartz usually contains fluid inclusions, fossil water that can be used to determine the temperature at which the veins formed. I want to know the relationships between the minerals and the gold, who’s first, who’s second, etc. Minerals are information to me.

Anyone discovering diamonds has a choice about what to do with that information. Do they withhold it, so they have monopoly on the sources? Good business sense, but not good scientific sense. Jeff shared data, and we got started on finding the source rocks. The burden of proof that these were North Carolina diamonds was clearly on him, and he was cooperative and helpful in working on the problem. I analyzed the other minerals that were panned with the diamonds, using the petrographic microscope and the SEM/EDS. We made thin sections of possible candidates for the source rock.  I was confident enough to make the recent announcement, but prudent enough to keep working on the problem. A quick check of my birth certificate shows that I wasn’t born yesterday.

I don’t think so much about “authentication” as much as I do about “reproducing results.” Science is a good discipline for separating out what you know, what you can surmise, and what you don’t know, and for building multiple working hypotheses to test along the way. I have the diamonds, I have some of the minerals from the streams. I have several working hypotheses about source rocks to target.

I can understand skepticism about the discovery of the diamonds. Even if we had TV cameras on Jeff as he found them, there would still be suspicion about the sediments being salted, or even that the diamonds were purchased somewhere else. If we can reproduce Jeff’s results that would be strong support that these diamonds are from North Carolina. Finding the source would certainly clinch the question.

Astute readers will notice that I have been very vague about location of this discovery. True. I have a responsibility as an employee of the state of North Carolina to preserve a good relationship with land owners. Field guides to collecting minerals or fossils in North Carolina tend to result sites being destroyed or placed off limits to collection. Most collectors in the state are very careful and responsible, but it only takes one bad one to ruin things for everybody.

Early next year, we will be crowdfunding the costs of the research. The work has several lines of inquiry: (1) identification of the inclusions in the diamonds; (2) field work to obtain more samples of heavy minerals from the streams; and (3) microanalysis of mineral separates taken from the streams.

Stay tuned. Next blog up, multiple working hypotheses and geological research.

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3 Comments leave one →
  1. Andrew permalink
    December 9, 2014 11:08 pm

    Because at least one of these diamonds contains what looks like a garnet inclusion, the geochemistry of that garnet and any other pyropes found in the associated heavy minerals from the stream shoud be analyzed for calcium and chrome. If the garnets are from a kimberlite or lamproite host, then the pressure temperature conditions of the intrusion can be evaluated based on the garnet chemistry. I woud suggest collaboration with Dr. Lawrence Taylor at UT Knoxville. He has an electron microprobe and is very experienced with diamond and garnet geochemical analysis.

    • December 10, 2014 11:13 am

      True, but we have electron microprobes in North Carolina. Before I went to the effort of polishing and probing one of the diamonds, I would try laser Raman microscopy, which does not require sample prep.

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