Slightly OT: Identifying rough diamonds?

[Itarub]

Hello all.

I don''t have much experience with precious gems, nor am I a jeweler or any other tradesman that would work with them, so I feel a little out of place here.

I was wondering if some of you might see fit to helping an under-informed outsider about an issue that you might have some significant insight into.

When I was a child, I spent a significant period diamond hunting down in Arkansas. Just today I chanced across a very large container that was filled with small crystals from my diamond hunting expeditions. I had never gotten around to identifying the various small stones that I sifted out of the earth, on the off chance that I might have an interesting keepsake mixed in with the bits of quartz, but I thought I might as well see what I could find regarding the identification of rough diamonds on the web.

This forum looked to be one of the best places to locate someone with experience in that area.

Any hints on sorting diamonds out of pounds of quartz? I have heard that the surface of raw diamonds is supposed to be much smoother than quartz, and that diamonds supposedly react under certain wavelengths of fluorescent light, but I have no idea how to go about sifting through this material.

I’m grateful for any help you might be able to provide.

 

[mike04456]

There is indeed a simple, cheap way to do it, but it's not foolproof. It's called a grease table, and it's how miners in the 19th century used to do it (and some still do). You'll need a wooden board about 2 feet square, a can of grease, and reservoir you can pour water into, like a child's plastic swimming pool or a big washtub.

Slather a good layer of grease onto the board and direct a broad, gentle flow of water over it into the reservoir. Drop a handful of your rocks over the board. The quartz will wash off, but the diamonds (if any) will stick to the grease.

This is not, as I said, foolproof, but anything that sticks to the grease is worth a closer look. Once you have it narrowed down, compare the heft of these stones with something that is obviously quartz. Diamond is significantly denser and any diamond crystals will be noticeably heavier for their size.

UV fluorescence is another way, if you have access to a UV lamp, but not all diamonds fluoresce. Blue fluorescence doesn't prove it's a diamond but it does mean it's most likely not quartz, which only has weak fluorescence, if any.

If you get to that point and still think you've got a diamond, it's time call in an expert.

Edited to add something else: any true diamonds you find are going to be very small, i.e., a few mm in diameter at best unless you're very very lucky. The mine in Arkansas has produced only a few stones over 5 ct, which is only 1 gram.

 

[Itarub]

Thanks for the info LawGem, I appreciate it. :}

 

[mike04456]

Well, don't take my word as gospel. There are others here who know a lot about the subject too. So I'd wait a day or two and see what other responses you get before setting up your grease table.

 

[mike04456]

Yes, x-ray fluorescence is the most reliable, but it is a tad expensive and complicated.

For those wondering, diamonds are often separated by illuminating them with x-rays. The Russians invented the process in the 1950s because their grease tables all froze solid in Siberia. It's an excellent method because it's fast and can be done by machine, unlike the grease belt/table process, which is labor-intensive.

S.G. liquid is also very simple but the 3.32 stuff (which you need for separating diamonds) is toxic and not good for newbies to be monkeying with.

It's best left to those who know what they're doing.

Of course, the great likelihood is that there aren't any diamonds in the jar anyway, given the very low grade of that deposit in Arkansas. But one can dream--that's what the gem business is all about.