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Colorado Prospector - Gem and mineral prospecting and mining forums _ Prospectors and Rockhounding Field Work _ Newby Cabin Fever Questions

Posted by: Easygoer Feb 7 2018, 09:44 PM

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It has been kind of quiet on the board lately! I am trapped in sunny Louisiana waiting for the summer to head to Colorado to start prospecting. Having nothing but time on my hands, or too much time actually I have some questions that I hope some of you would be kind enough to answer if possible. Newbie questions to be sure but I haven't seen them answered elsewhere and they seem to be somewhat specific to the Colorado area. So here goes!!

" The Arkansas River has very fine gold mixed with black sands, what is the black sand? Reading about it on the internet (I know that can be dangerous) it could be several different things, does anyone know what the Arkansas holds?

" What are waste materials are typically found with the gold, meaning when you have classified down to where you are separating out the gold, what else is left in the pan? Garnet? Lead? I know depending on the area you prospect these will vary, I will be in the Arkansas River.
" The reason I ask is has anyone tried upgrading their cons to see if you can capture a higher percentage of the ultra-fines. Specifically has anyone tried the rod mill detailed by Randy Clarkson. I have two PDF documents that he sent if anyone would be interested in seeing them. Basically, cons are run for 7 minutes in the mill, contents screened to remove large flattened gold pieces, the remaining contents can be rerun on a finishing table, the rod mill will have flattened the gold and allow for additional recovery, above 90% in his trials. According to his findings some of those coffee cans contain gold in the amounts of 50,000g/mt.

" Again, I know there is no absolute answer to this question, I am just curious what size is the fine gold typically found? I know the "big" could be anything, but how small is small? Is there any value to increasing the % recovered or is there not enough there there?

" Back to the black sands, I know black sand can be present without gold, but apparently in the Arkansas black sand and gold seem to go together. In one of the posts (I believe it was Crusty, couldn't find it again so if this isn't correct sorry) there was concern that the black sand would overwhelm the dredge sluice box very quickly. If this is the case has anyone ever tried to further process this black sand to see if there is micro-fine gold in the sands? By further process I am referring to some type of grinding in a mill or other mechanical methods?

Any answers to any parts of these questions would be greatly appreciated! I am not sure as to the appropriateness of attaching links or embedding PDF's if it is not an issue and anyone would like to read them I will be glad to post them.

Thanks

Easygoer

Posted by: johnnybravo300 Feb 7 2018, 10:24 PM

Nice snow! That's about all we've gotten this year and its usually waist deep by new years. Weirdest winter ever.

I'm not an expert on the ark but have prospected a few different places and been to point barr. All the gold I've found has been super fine or flour gold. Tons of black sands, more than I've ever seen anywhere else and by far. There is visible black sands many places in the shallows and eddies right on the surface and it contains everything you can imagine. Your cons will be full of gold that is too small for the eye to see and even smaller gold than that flows down in the currents 24/7 in that river. It's like a 200 mile long ball mill that's seen the wrath of God flow down it numerous times in past torrential floods.
So many mineralized tributaries flow into the ark for the entire length down from the headwaters that anything could be found in it although it's usually crushed in the process. There's alot of sand also because of this.
I've never dredged there but I hear they do the best getting out in the current and the deeper water. I have a buddy that got 1/2 oz in one day on the ark dredging a virgin spot and it was his best day ever. He said he had over 60 lbs of weights strapped to him and had to roll boulders in the current that would have crushed him and he's no little fella. Not the smartest thing but he does the best going where others won't.
There's plentiful bedrock exposed in many areas as the river cuts though multiple different layers and even the high benches could hold deposits along there anywhere.
There's also mercury in some places and lots of fishing weights, lures, cans, cell phones, car keys, you never know and it's well used by fishermen and rafters.
I haven't dug there enough to notice consistencies except that it can be very spotty. Just takes time to figure it out and that's half the fun.
The area you're going to may be different but that's what I've found. Sorry no better details but hope it helps and good luck.

Posted by: ASTROBLEME Feb 8 2018, 03:12 AM

Hi Easygoer,

You might be onto something with the milling idea. I've never heard of anyone trying that out on Arkansas River concentrates.

Most of the black sand in the Arkansas will be Magnetite but a small portion is at best, only very weakly magnetic. This material is exceptionally hard to deal with when processing the concentrates as it doesn't stick to magnets that are used for separating out the fine heavies. When I've looked at the non-magnetic sands with the microscope, they appeared to be Ilmenite. I've never had any of the black sands assayed as I thought that they weren't of much value since they were so prolific. A good source for more info on Ilmenite is linked below;

https://geology.com/minerals/ilmenite.shtml

Much of the source gold found in the ore emplacements near the Arkansas Headwaters was very fine to start with. The miners working the South London Mine east of Leadville had to crush the ore to a very fine size to properly extract the tiny specks of gold. Those tailings were so fine that they would flow easily out into waste ponds when mixed with a little water as shown here;



ASTROBLEME

Posted by: Easygoer Feb 9 2018, 09:19 PM

QUOTE (ASTROBLEME @ Feb 8 2018, 03:12 AM) *
Hi Easygoer,

You might be onto something with the milling idea. I've never heard of anyone trying that out on Arkansas River concentrates.

Most of the black sand in the Arkansas will be Magnetite but a small portion is at best, only very weakly magnetic. This material is exceptionally hard to deal with when processing the concentrates as it doesn't stick to magnets that are used for separating out the fine heavies. When I've looked at the non-magnetic sands with the microscope, they appeared to be Ilmenite. I've never had any of the black sands assayed as I thought that they weren't of much value since they were so prolific. A good source for more info on Ilmenite is linked below;

https://geology.com/minerals/ilmenite.shtml

Much of the source gold found in the ore emplacements near the Arkansas Headwaters was very fine to start with. The miners working the South London Mine east of Leadville had to crush the ore to a very fine size to properly extract the tiny specks of gold. Those tailings were so fine that they would flow easily out into waste ponds when mixed with a little water as shown here;



ASTROBLEME



I am completely ignorant as to how to post on this board how do you attach PDF files?

Thanks

Easygoer

Posted by: Crusty Feb 9 2018, 10:41 PM

Not saying it isn't possible, but with the amount of black sand on the Arkansas, if it held significant gold, there would be a lot more folks collecting and processing it. I'd get it assayed before i imvested too much time and effort in to milling it.

To manage the amount of black sand, you need to adjust the amount of material you suck to give the Sluice a chance to clear out the black sand.

Posted by: Easygoer Feb 10 2018, 10:40 AM

QUOTE (Crusty @ Feb 9 2018, 10:41 PM) *
Not saying it isn't possible, but with the amount of black sand on the Arkansas, if it held significant gold, there would be a lot more folks collecting and processing it. I'd get it assayed before i imvested too much time and effort in to milling it.

To manage the amount of black sand, you need to adjust the amount of material you suck to give the Sluice a chance to clear out the black sand.


Crusty,

I know your new claim is just North of me on the Arkansas, so we would probably see similar a similar composition of black sands when dredging. How much concentrates do you end up with when running your dredge? Guesstimate of weight per hour of operation? The reason I ask is a 10" rod mill processes about 1- 1.5kg every 8 minutes on average. If someone can list the steps to post a PDF I would be glad to post both documents.

I saw some of the gold you recovered at the end of last year, what size would you estimate these pieces to be? The reason I ask is the rod mill takes advantage of the malleability of gold to flatten the smaller pieces, so they don't escape through screens and can be recovered.

Appreciate your time on this, supposedly "the only dumb question is the question you don't ask", my wife would argue with that for sure where I am concerned!

Thanks,

Easygoer


Posted by: Denise Feb 10 2018, 11:39 AM

You have a beautiful home Easygoer! For uploading a PDF you will need to click the "CHOOSE FILE" button (Below the text box to the right) and click on the PDF you want. Then click the "UPLOAD" button. The PDF should then be attached to your post and ready to go. happy088.gif

Posted by: Easygoer Feb 10 2018, 01:14 PM

QUOTE (Denise @ Feb 10 2018, 11:39 AM) *
You have a beautiful home Easygoer! For uploading a PDF you will need to click the "CHOOSE FILE" button (Below the text box to the right) and click on the PDF you want. Then click the "UPLOAD" button. The PDF should then be attached to your post and ready to go. happy088.gif


Denise,

Thanks and thanks  ubc_2016_february_clarkson_gavin.pdf ( 2.05MB ) : 1366

Posted by: Easygoer Feb 10 2018, 01:18 PM

QUOTE (Easygoer @ Feb 10 2018, 01:14 PM) *
Denise,

Thanks and thanks  ubc_2016_february_clarkson_gavin.pdf ( 2.05MB ) : 1366





 150709_Instructions_for_Rod_Mill_Use.pdf ( 817.59K ) : 95
 

Posted by: Crusty Feb 11 2018, 06:16 PM

QUOTE (Easygoer @ Feb 10 2018, 09:40 AM) *
Crusty,

I know your new claim is just North of me on the Arkansas, so we would probably see similar a similar composition of black sands when dredging. How much concentrates do you end up with when running your dredge? Guesstimate of weight per hour of operation? The reason I ask is a 10" rod mill processes about 1- 1.5kg every 8 minutes on average. If someone can list the steps to post a PDF I would be glad to post both documents.

I saw some of the gold you recovered at the end of last year, what size would you estimate these pieces to be? The reason I ask is the rod mill takes advantage of the malleability of gold to flatten the smaller pieces, so they don't escape through screens and can be recovered.

Appreciate your time on this, supposedly "the only dumb question is the question you don't ask", my wife would argue with that for sure where I am concerned!

Thanks,

Easygoer


First step is to see if the black sand is containing gold. No point in putting together a rod mill until you know if there is value.

Hard to compare the amount of cons between 2 dredges. The sluice will only hold a limited amount of cons. Will vary by sluice. Every thing in excess of the sluice capacity will exchange out, leaving only the heaviest material.

Average gold size is around 30 mesh, with quite a bit smaller and much less bigger.

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