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Tools to identify diamonds

Posted by Diane Kniskern  
Diane Kniskern January 20, 2010 09:37PM
There are many brands and models of "diamond detectors" available online. Does anyone know what kind would be the most reliable to test rough stones found at the Crator of Diaminds in Arkansas? I've looked at the thermal conductivity models and I like the ones which claim to identify colored gemstones, as well as diamonds, but I don't know how much I need to spend to get an accurate one (or if they work at all). I've also looked at refractive index testers and thought the two might be a good combination. Does anyone have experience with any of these? Thanks.
Alfredo Petrov January 20, 2010 09:43PM
Diane, if you familiarize yourself with the appearance of natural diamond crystals, you won't need the testers - Rough diamonds are visually distinctive. Start with the photos here on Mindat. The staff at Crater of Diamonds should be able to teach you more.
Furthermore, the refractometers and thermal conductivity testers that jewellers use are designed for use with polished surfaces; they won't work so well with the rougher surfaces of natural uncut crystals.
Dean Allum January 21, 2010 12:56AM
A UV lamp, or the thermal conductivity detectors already attached to your hands are less expensive than the gem meters.
-Dean A.
Matt Neuzil January 21, 2010 03:09AM
I am not familiar with the cost of RI fluids but I think some scrap corundum would at least work for a scratch test... and should rule out anything else.

A buena hambre no hay pan duro
Alessio Piccioni January 21, 2010 09:09AM
I agree Matt Neuzil, sometimes i use the same sistem for identify cut diamonds from cut zircon. Remember Diane, the diamonds are the only stone resistant to carborundum scratch.

Edited 1 time(s). Last edit at 01/21/2010 09:09AM by Alessio Piccioni.
Diane Kniskern January 24, 2010 05:02PM
Thanks for the replies, but I still need an answer to my question about which testing devices are most reliable.

Having been at the Crater of Diamonds many times and having seen numerous diamonds found there over the years, I am quite familiar with the appearance of natural diamonds. If I were lucky enough to find something like the 'Easter Sunrise' or the 'Okie Dokie,' I would agree a tester is unnecessary. However, diamond finds of that magnitude are extremely rare at the Crater.

Though I do appreciate your suggestions: most of the finds are far too small to test for coolness with your fingers. Not all diamonds are florescent. Due to the extreme brittleness of genuine diamonds, doing a scratch test could easily shatter them, so it is not recommended. In addition, though some rough diamonds (like Billy Moore's 'Frosty') do have rough surfaces, many have a natural highly polished surface conducive to thermal testing. I also have colored crystals from North Carolina I would like to test.

The Crater's Diamond Discovery Center has wonderful interactive exhibits, demonstrations, and videos, and the staff there does a great job educating the public. Some staff members try to take the time to identify each speck of mineral brought to them, but when it gets busy in the summer, it is nearly impossible for the staff to closely examine all the tiny shining crystals clutched in the sweaty hands of hopeful visitors waiting in line, especially at closing time. It's easy to understand why, after identifying a hundred handfuls of calcite and quartz, a tired staff member might just give a quick glance and say, "Calcite and quartz."

I have several small stones I would like to test which visually appear to be diamonds. They are probably too small to be cut or have much value, but I wouldn't sell them anyway. I would just like to know for sure. I have photos, but don't know to submit them. Alfredo, if you can identify diamonds by sight, please tell me how to get photos to you. Thanks.
Alfredo Petrov January 24, 2010 10:12PM
Diane, your Mindat access has already been activated, so you can upload any photos on your computer into Mindat. Just go to the Mindat Manual at:
...and then click the line about uploading photos, for instructions.
When you are using Mindat, you should see a button in the top left hand corner of the scren - "My Home Page" - Click on that and your own personal space on Mindat will be accessed (Yours is still empty). You can upload photos, articles, blogs, there.
Diane Kniskern January 24, 2010 11:36PM
OK, I put three pictures on my page (I think). Hopefully I did it correctly and didn't break any rules.

Edited 1 time(s). Last edit at 01/25/2010 12:30AM by Diane Kniskern.
David Von Bargen January 25, 2010 02:07PM
If you just want to upload photos to the messageboard, just click the "Attach a file..." link in the gray area above the new message entry box.
Diane Kniskern January 25, 2010 03:41PM
Thanks, David.

The tiny crystals in the attached photos (shown in a 2 & 3/4 inch peanut butter lid) are all about 1/16 inch in diameter. I collected them two weeks ago near Murfreesboro, Arkansas. Do they look like diamonds (though too small to be of value) or just quartz?

PS: What is the best material on which to photograph tiny minerals?

Edited 2 time(s). Last edit at 01/25/2010 03:56PM by Diane Kniskern.
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Lachrisha Smith January 25, 2010 06:07PM
Diane, I bought a tester and it has all the stuff. after a few yrs. of mineral collecting I realized my eyes were better for identification on most my minerals. although it is great for cut stones,..I dont recommend it for rough.its important to visually rely on your the rough stones will be easily identifiable through scratch test and crystal form, I think. accsesory minerals can also help in identifying a mineral species.The diamonds at crater park could be seeded as I have heard. either way , diamond rough here on mindat, and remember nothing sticks to a diamond and they do feel greasy.I did look at your pictures and it looks like quartz to me. hope this helps. and the tester most used is a presidium duotester : (presidium instruments usa 255-4 big run road lexington ky 40503) is where i got mine, but you can get them anywhere. best wishes, Lachrisha
Diane Kniskern January 25, 2010 06:34PM
Lachrisha, thanks for answering my question!

I've often wondered if any of the larger diamonds found at the park might be seeded (the ones in the photos sent out in the email newsletter that cause me to drive back to the Crater from Virginia), but I've seen quite a few small ones actually being found, so I know they are there. I found the crystals in my photos outside of the plowed search area. Guess I'll go 'turn the jar over' and see if they fall out of the peanut butter! Diane
David Von Bargen January 25, 2010 09:14PM
The park itself isn't doing any salting. Some people have been known to bring in some diamonds and say they were found there.
James Christopher January 26, 2010 01:12AM
Lachrisha Smith Wrote:
> The
> diamonds at crater park could be seeded as
> I have heard. either way , diamond rough
> here on mindat, and remember nothing sticks to a
> diamond and they do feel greasy

Don't diamonds stick to grease?
Steve Hardinger January 26, 2010 03:01AM
The specimens in the pictures look to me like quartz. They do not appear to have the somewhat greasy luster of natural diamonds. But then again, photos can be deceiving.
Diane Kniskern January 26, 2010 07:48PM
Speaking of which, whatever happened with Eric Blake? I haven't heard anything about it since last year.
Jamey Swisher April 21, 2010 08:52AM
First off, any and all testers for colored gemstones are not going to be accurate plain and simple as they can not tell the difference between a synthetic and a natural stone and often times stones also overlap so it can not distinguish between certain materials. These devices are really only worthwhile, accurate, and useful to those with an education in Gemology and when used in conjunction with other tools. That said, the Presidium Reflectivity tester is one of the better units out there, especially with the extended chart converting reflectivity index to refractive index. But again, it is only useful to tell the difference between certain materials, like diamond and cz or the like, and such without training and without being used in conjunction with other tools.

A nice hydrostatic specific gravity setup would be far better and more useful for ID'ing gemstones. Especially combined with a refractometer or reflectivity meter.

Registered Gemologist
Research Gemologist
Club President/Owner
FDray October 27, 2011 04:21PM
Yes pic 0058 has 3 diamonds, middle right, lower left, and lower center. 0054 has three, maybe four, top three for sure, and maybe lower left. without a loupe would be hard to tell on that one. 0049 has one the others are to blurred to see. A simple test is with a small red lazer, put the stone on bright white printer paper in the dark. With the lazer in front of you, so no light is bounced back to your eyes if it is a diamond, put the lazer right on the stone with the lens touching. Put a beam through the stone, the crystal structure of a diamond will bounce the beam and split it inside to make it glow red with bright points of light, quartz will pass the beam, much like glass.
FDray October 27, 2011 04:41PM
Diamonds will only stick to grease in a sluce, or in water. Diamonds are hydrophobic, none wetable, so will stick to grease in water. All other stones have a wet surface so they have no contact with the grease.
John Betts October 27, 2011 05:18PM
A UV lamp is NOT a good tool for identifying diamonds. Diamonds fluoresce when activated by X-rays. But of the thousands of diamonds I've sold only a handful fluoresced under Ultra-Bright SW UV.

Any diamonds found at Crater of Diamonds should be certified by the Park Service where they will issue a certificate about the size of a business card verifying that it is a diamond and the weight.

Lastly, almost any jeweler will have a diamond tester that measures thermal conductivity and can distinguish between diamond and simulants. There is no need to buy a tester, just befriend your local jeweler.
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