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Best Way To Recover Diamonds And Sapphires In Dry Gravel?


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Hi Jim, thanks for the responses. What a coincidence that I see your video and you not only happen to be working in my part of the country but also a member of this forum! 

1 hour ago, Jim in Idaho said:

Back on the gem recovery, dry. There is no way, using gravity, to recover gems dry. Can't be done....

This was the part I had a question on, but after a bit of sleep I may have answered it myself. In your videos you said the jigs work great on gems, but then later change your mind and say they don't work. I am guessing what you meant in the videos is that they work great on gems when running wet but that they don't work well running dry?

1 hour ago, Jim in Idaho said:

Trouble with this, Jasong, is all you'll build is a classifier. You'll just collect all the gravel sized between the oversize screen and the undersize screen.

It's definitely a classifier, but it's also vibrating/jigging so the idea is that if the gravel is classified in a way such that the average size of the gems is always smaller than the average size of the gravel, the granular convection effect will actually help since it will keep the smaller particles at the bottom (gems) and the larger particles convecting up to the top (gravel). The oversize classifier lets in gravel bigger than the largest expected gems, the undersize classifier removes the smaller gravel/silt so that the gems are now among the smallest particle size in the mix.

That's the theory anyways. Of course, you can never know what sizes of gems you might be recovering so there will be gem losses out of the bottom classifier, and in some cases you might lose a really large gem too if it's close in size to the largest gravel, and so this idea would not work well where the sizes of the gems is mostly tiny or highly variable. But in areas where say most are bigger than 20 mesh, but smaller than 1/4", then they should not convect up to the top if you have gravel up to 1/2" in there as well. So, it's a matter of strategically selecting screen sizes. Also, the undersize screen will also basically "deslime" all the silt and whatnot out, an added benefit for later cons cleanup.

That's the idea anyways, of course ideas never work as expected when put into practice and built. :smile: It'll have to be a winter project for me as I don't have enough time right now to build such a thing to see if it'd work or not. 

1 hour ago, Jim in Idaho said:

Here's another thing to throw your way....the shape of the container has a large bearing on GC, and can actually make GC work in reverse, in some instances.

Interesting, can you elaborate on that a bit more? I watched your vid on the circle jig and GC seemed to still be occurring, it must be another shape? Or potentially it reverses at the edges?

Well maybe see you out in the field sometime, if I get some kind of machinery to actually work you could come take a look. We'd probably have a lot to talk about.

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Thinking on this thread and Jim's experiments a bit more, I think I'm going to leave the drywasher at home though.

Seems like the best (simple) way dry is just a 20 mesh hand classifier to get rid of silt, a 3/8" to get rid of the oversize (I don't predict any gems larger than 1/4" here), then dump all the oversize onto a big tarp and just smoosh it out by hand and look for anything shiny, colorful, or out of the ordinary and pick it out with fingers.

Or, just bag up all that classified material and run it through my Gold Cube at home later if that cut is small in volume and easy to collect/transport.

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Jason, 

Recommend you call Mark Keene, they sell commercial Diamond and Gemstone dredges for overseas ops and have probably studied the subject thoroughly. I'm sure they have looked at dry projects also. He likes to share his extensive, expert knowledge!😀

Bill

image.thumb.png.ec5013d288ce716a2991d7213c9cd624.png

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6 minutes ago, cobill said:

Jason, 

Recommend you call Mark Keene, they sell commercial Diamond and Gemstone dredges for overseas ops and have probably studied the subject thoroughly. I'm sure they have looked at dry projects also. He likes to share his extensive, expert knowledge!😀

Bill

Hmm not a bad idea, yeah I'll see if he's come up with any interesting dry gizmos.

I just ordered a wide array of 5 gallon classifiers so I can get an initial trip done as I'm rearing to go investigate some research right now, but this winter, a gem recovery building project sounds like a fun way to spend some time when snowed in.

Like 20 years ago or whenever it was when I met you when we were all dredging, I found what I suspected to be a diamond. It came from another smaller tributary that I was test panning on my way back home though. It would scratch anything I could find and nothing would scratch it. That thing sat in the little change nook in my truck for years and years, kept meaning to get it tested. One day I realized it was just gone, couldn't find it anywhere, think it fell on the floor and I vacuumed it up. It haunts me to this day hahaha. I think it was actually sapphire though, not diamond, now that I've seen a lot more, but I'll never know.

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Testing my initial dry jig, I recovered some garnets, and thought it worked for gems, but later determined it was because the garnets were smaller than the rest of the material. When i realized that, I corrected things, so people didn't think it would work for gems. That was a few years ago, and I've learned a lot since, too. The real basic problem is the fact gems are only about 50% heavier than the background material. We are asking a lot of a machine to separate them by gravity with that tiny difference. It's possible a machine could be built to do that, but it would require adapting the unit for each gem type, and each background material...a real PINTA, and losses would probably still be high.

For diamonds, a dry screen is dandy. It's best to pick them out dry anyway, as they sparkle even when dry, and everything shines when wet, so tends to mask the diamonds.

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Jason, 

I'm sure you've read some of this, but thought I would share some of Dan Hausel's work:

https://gemwy.blogspot.com/2011/08/wyoming-is-number-one-gemstone-state-in.html

Bill

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Yep, read all of Hausel's stuff long ago. Definitely a lot of good information to get started. Most of what he wrote about was just field investigating stuff in the WSGS files or old various reports to sent to them though, near as I can tell, so I've found it's best just to locate those original reports directly and sometimes therein is information there which Hausel didn't publish, which leads to other things, which leads to other things, etc and few people have found that stuff. 

Here's some pale blue sapphire in vermiculte/mica that I discovered in situ in a place you won't find in any writings today. As far as I know, I'm the only person who has found this area in modern times, though there is an old prospect pit which appears to be from the 30's so I wasn't the first. This is mostly reaction rims, with small pale blue sapphires buried deep inside each one. You can only see the reaction rims in the photo mostly, it takes quite some work to get the sapphires out, and unfortunately they are usually fractured (much like the more well known red rubies of WY). I plan on working the dry washes under this deposit for placer sapphires to see if it's easier to recover a lot of them that way.

So far nothing I would consider gem grade though as the Wyoming Craton contains among the oldest rock in the world and has undergone a substantial amount of both tectonic movement as well as various stages of metamorphism or just plain old chemical/weathering alteration for billions of years, and so a lot of stuff tends to change or get shattered unfortunately. 

image.png.544952832b2171559b12bffbbfea8800.png

 

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I have used a highbanker to prospect for diamonds when I lived in WYO.  I had varying results recovering indicator minerals and never found anything I thought was a diamond.

I have thought about making a recirculating sluice/grease table.  A portion of rifles in the top part first for indicator minerals and diamond with a lower section of grease table.  From things I have read there are problems with grease tables such as temperate of the water and organic material.  To warm the grease mixture washes out.  To cold it gets harder and diamonds won’t stick.  Organic carbon can cover the entire grease section preventing diamonds from sticking.  Also diamonds may not adhere because of stuff coating them.  I though about using a hot water heater to maintain the right temp for the water in cooler times of the year.  Like mentioned, I would screen off large material above a 1/4 inch and likely everything below 16 mesh, maybe a little smaller, prior to tuning it through.

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Have you seen Dan Hurd describing gem sieving?

how to pan for garnets youtube

 

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3 hours ago, Bear said:

I have used a highbanker to prospect for diamonds when I lived in WYO.  I had varying results recovering indicator minerals and never found anything I thought was a diamond.

Working lamproites or kimberlites? For diamonds, my intention was to explore all those lamproites since they appear underexplored (also hence the total lack of water out there). Working wet is not an option to me. 

1 hour ago, GotAU? said:

Have you seen Dan Hurd describing gem sieving?

I hadn't, though Dan Hurd is one of the few prospecting channels I do occasionally watch. But he is on a river here. Working with water and gems is much easier. He's using a saruca basically, or in other words doing a sort of hand jigging similar to the process Off Grid posted, except with no machine. Also, in his case the sand is already filled with garnets in every handful. Some places I want to explore will be like 1/4 to 1/2 yard of dirt to maybe 1 gem, it's quite a bit harder to recover the latter vs the former, the lack of water makes it more so.

Processing the amount of dirt I need to process would just require a crazy amount of water hauling if I did that in a tub, and the remoteness makes hauling water infeasible in any quantity. Wyoming is similar to Nevada in terms of remoteness of some areas, except often the roads are rougher/rockier since there is less "basin", and a lot of "range" (or rocky hills), comparitively. 

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