# Process for large amounts of black sands needed.



## Placer Paul (Nov 25, 2017)

I'm a small scale placer miner. I have been doing exploration mining for the past few seasons and will be increasing to small production mining.

I am trying to figure out the best way to process my black sands after they have been run on a finishing sluice and a miller table to get the visible gold out.

I have had the black sands assayed after I have gotten the visible gold out and the assays have averaged at 60 gr/ton gold. 

A lot of the gold in the black sands is locked in the black sands. Like coated inside the black sands. I have not yet gotten an assay that shows what minerals are in the black sands. The assays I have gotten so far I just asked the lab to give me the gold value in it. I do plan on getting a full analysis done though for other precious metals and all other elements. 

My black sands on the average weigh around 92 lbs per 5 gallon bucket. This works out to approximately 2.76 grams gold per 5 gallon bucket of black sands.

I will be producing approximately a 5 gallon bucket of black sands every 5 days or so.

I am wondering what the most economical, least time consuming, and efficient way would be to extract the remaining gold from the black sands after I have gotten all the visible gold from it that I can.

I am thinking that my choices are: 
1. Grind the black sands to a powder. (some miners are putting them in cement mixers with ball bearings and pulverizing them while still keeping the micron gold intact) then running them on a shaker table
2. Smelting to get the gold bead.
3. Grinding to powder then leaching.
4. Stock pile them and pay a refinery to do it. 

Am I correct in this assumption that those would be my options? Do you suggest any other options? Do you need to know a full elemental assay result in order to give me an appropriate answer?

If the best way would be the cement mixer then shaker table then I know how to do that no problem. But if smelting or leaching are better ways can you please let me know what kind of equipment and supplies I would need for the process so I can do some math and see if it's economically feasible for me to do so?
In my rough math estimates I should be able to extract approx $3000-$5000 worth of gold per season from my black sands minus equipment costs to do so. So this can help me pay some of my operating costs for the year. There's also a good chance after buying the supplies to do this with that other fellow miners in the area may pay me to process their black sands to help me recoup some of the capital costs for the equipment. A few of them I know have just been stock piling the black sands and have been waiting to process them.


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## nickvc (Nov 26, 2017)

I am far from an expert on mining but my view would be to use whichever process would be the least time consuming for you as time will be money which is why others have simply stockpiled their black sands.
Your best advice may well come from Deano or Reno Chris if they read your post as they both have good experience in this field but it might be that there is no best method with all options having some advantages and some drawbacks.
If you do well in your new mining venture please keep us informed as it’s rare for us to read and see success from our mining members.


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## IdahoMole (Nov 26, 2017)

From what I understand from reading the forum is leaching is not the way to go.
I would try gravity separation first. It sounds like you are set up to pulverize the material and run on a concentrating table so give it a shot and see what kind of recovery you get. 
Smelting is often used on black sands but coming from someone that has never done that it doesn't seem economical to smelt 5 gallons of sand for a few grams of gold. Time, materials and supplies would add up. I could be wrong? 
That leaves stock piling and sending out to a refiner. Which also leaves you free to do more mining. 
Just my thoughts


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## Deano (Nov 26, 2017)

Your first approach should be to do a really careful magnetic separation of your sands.

When this is done you get the mags and non-mags weighed and assayed separately.

The results from this tell you what steps to take next.

Deano


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## Placer Paul (Nov 26, 2017)

Thank you everyone for your replies.



Deano said:


> Your first approach should be to do a really careful magnetic separation of your sands.
> 
> When this is done you get the mags and non-mags weighed and assayed separately.
> 
> ...


Ok thank you Deano. What kind of assay should I ask for, for the magnetic and non magnetics? Should I do a separate assays like one for just gold, one for other PGM's and one for multi elements?


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## Reno Chris (Nov 26, 2017)

Whole material smelting is not likely to be an option with such low gold content. 
Assay both fractions, magnetic and non magnetic. 
As Deano says, this will tell you a lot of what you needed to do. 
Its likely that the non-magnetic fraction can be lightly pulverized and run a second time across the table - but the assay is necessary to say for sure. 
Tables do not get 100% recovery, and with a little pulverization will probably allow another percentage to be recovered.


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## Placer Paul (Nov 26, 2017)

Reno Chris said:


> Whole material smelting is not likely to be an option with such low gold content.
> Assay both fractions, magnetic and non magnetic.
> As Deano says, this will tell you a lot of what you needed to do.
> Its likely that the non-magnetic fraction can be lightly pulverized and run a second time across the table - but the assay is necessary to say for sure.
> Tables do not get 100% recovery, and with a little pulverization will probably allow another percentage to be recovered.


Thank you Chris. I will do some more assays after separating. You mention that perhaps I can get more gold out of the non magnetic black sands after pulverizing and re running but is that not possible to also do with the magnetic sands? I know I need more assays but I am interpreting that you may mean pulverization may not be possible with the magnetics?


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## Deano (Nov 27, 2017)

Unless you have hit a most unusual deposit there will be little value in assaying for anything apart from gold.

Dreams of high level ppm values for pgms are usually just that.

Black sands are most unlikely to contain viable grades of silver, just get both fire and aqua regia assays for gold on the two fractions.

Review future processing when you have these results.

Deano


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## Placer Paul (Nov 27, 2017)

Deano said:


> Unless you have hit a most unusual deposit there will be little value in assaying for anything apart from gold.
> 
> Dreams of high level ppm values for pgms are usually just that.
> 
> ...


Will do. Thank you


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## im1badpup1 (Nov 28, 2017)

Im new to this myself but wouldnt very thorough classifying and sizing of your material to a uniform particle size be the way to go in concentrating your blacksands down to a better concentration volume?

If your remaining gold values are encapsulated in differing blacksand materials eg oxides sulfides tellurides of magnetite hematite etc to reduce loss and make processing easier id grind to a smaller uniform particle size where most of my volume of material is ground to as fewer different sizes as possible. The smaller the particle size the more the density of gold comes into play and should minimise losses.
Makes it easier once your machine is dialled in with correct flowrates to have only eg 3 sizes not 30 to have to adjust to.

Have you actually identified encapsulated gold under a microscope?
Its definately not invisible free gold that u can only see when tapping a heap together in the pan?
You reaĺy could do with knowing what its coated with cos if its iron oxide only or not at all magnetic separation would be a good start.
Then look towards chems to.free it but first your volume needs reducing by 90-95%

If you find some encapsulated gold put a drop of acetic acid (vinegar) on it warm to 50c if its iron oxide youll dissolve the oxide to acetate and get a green solution.
Nickel oxide also dissolves to nickel acetate giving a green solution.

If the majoritys in the magnetics you can separate them again by using a weak magnet to pull iron oxides but not nickel. and a n52 picks up everything


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## Reno Chris (Nov 28, 2017)

> Thank you Chris. I will do some more assays after separating. You mention that perhaps I can get more gold out of the non magnetic black sands after pulverizing and re running but is that not possible to also do with the magnetic sands? I know I need more assays but I am interpreting that you may mean pulverization may not be possible with the magnetics?


No, that's not what I meant. Its likely that a significant majority of the gold will just naturally be in one fraction or the other. If 80% is in the non-magnetics then you focus on them. If the majority is in the magnetics, then you focus on them. You will not be getting 100% recovery and you must accept that. Even big operators who do vat leaching with cyanide on ores only get maybe 97 or 98 percent recovery. There is a point where you can spend 10 hours and hundreds of dollars to get $50 worth of gold. That kind of effort is silly. 

Tables and jigs do not get 100% recovery. Years ago in the early 1980s, I had the opportunity to tour the last dredge operating at the Yuba goldfields near Marysville, California. St. Joe minerals was the operator of the bucket line dredge and produced a couple tons a day of back sand. After processing, they turned the sand over to the property owner (St Joe minerals leased the property). The owner did nothing to the black sand other than reprocess it back over another shaker table that he owned. He averaged 3 ounces of gold per day.


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## anachronism (Nov 28, 2017)

Chris has nailed one of the constants of gold recovery here. The last few percent of any recovery often costs more than the gold is worth. The same applies to e-waste.


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## im1badpup1 (Nov 28, 2017)

Chemical synthesis and extraction is the same. The last few % is uneconomical to chase so its either left or added to a stock and a single pull done when its worth it.

Have you tried using a goldcube on the concentrates? Im suggesting it because you can feed a ton through in an hour or just over of prescreened material and be left with a couple kilo of concentrate thats it.
Having uniform particle size and reducing the flow rate so it only just passes material through is key. 
Im feeding mine whats already a concentrate of blacksand screened to 1/8th but the smaller and more uniform size material u go the better it performs adjust flow rate slightly. Raising the pipe level or cloth around the intake if you havnt a valve fitted will do.
Put it all through in one go from what i can gather it works best exchanging lighter for denser particles and concentrating that way.
Il show u a pic after 3 buckets of fine black sand my cube looked bunged up but it was in fact working well with water running still trapping micron gold actively


Then look at that concentrate under microscope grind the cr ap outter some and see if your encapsulated golds there in quantity or not.

Have you a couple pics of your concentrate to get an indication of its composition?


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## Placer Paul (Nov 28, 2017)

im1badpup1 said:


> Chemical synthesis and extraction is the same. The last few % is uneconomical to chase so its either left or added to a stock and a single pull done when its worth it.
> 
> Have you tried using a goldcube on the concentrates? Im suggesting it because you can feed a ton through in an hour or just over of prescreened material and be left with a couple kilo of concentrate thats it.
> Having uniform particle size and reducing the flow rate so it only just passes material through is key.
> ...


Hi there. Thank you for your reply. Well ya, I have to re assay my black sands with some of the larger material assayed separately from the very fine black sands. Cause the lab ground the sands to a powder then assayed for the gold. So in reality I don't know how much of the gold is trapped inside the larger black sands and how much of it is just very fine micro gold sitting freely in the black sands. I have not used a gold cube yet. Normally my procedure is to do three classification sizes of the black sands then run them on a clean up sluice, then run the cons from those three runs on a miller table to get the very fine gold out. It's a long procedure when there is lot's of black sands to do.

How fine of gold can the gold cube catch? Have you had your black sands assayed after running through the cube to see if it is catching all of the gold or if there's still gold in the black sands afterwards?
So even if the material is pulverized the gold cube won't get clogged up with the fine powder?

I know for certain that some of my gold is actually coated by black sands minerals cause my neighbor miner has pulverized theirs and freed trapped gold after the pulverizing. 

I have requested a mineral microscope for Christmas from my wife lol. Currently I only have a little hand held 30x scope and a usb microscope. Neither is very good at showing the material cause of the light that automatically comes on when turning them on. The minerals reflect the light badly. 

Here are some pics of my black sands. There is larger classified, finer classified, and pulverized. Note that there is a small amount of small metal filings in some of the larger classified black sands cause I had done some drilling/welding work on my trommel while the sluice was still attached and forgot to clear the filings from the system before I started running the wash plant again.


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## Placer Paul (Nov 28, 2017)

Reno Chris said:


> > Thank you Chris. I will do some more assays after separating. You mention that perhaps I can get more gold out of the non magnetic black sands after pulverizing and re running but is that not possible to also do with the magnetic sands? I know I need more assays but I am interpreting that you may mean pulverization may not be possible with the magnetics?
> 
> 
> No, that's not what I meant. Its likely that a significant majority of the gold will just naturally be in one fraction or the other. If 80% is in the non-magnetics then you focus on them. If the majority is in the magnetics, then you focus on them. You will not be getting 100% recovery and you must accept that. Even big operators who do vat leaching with cyanide on ores only get maybe 97 or 98 percent recovery. There is a point where you can spend 10 hours and hundreds of dollars to get $50 worth of gold. That kind of effort is silly.
> ...


Ah ok got it thank you for clarifying. Ya I'm all about making a profit and not wasting time if it's not worth it. Mining has tough enough margins even with decent ground these days.


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## Placer Paul (Nov 28, 2017)

anachronism said:


> Chris has nailed one of the constants of gold recovery here. The last few percent of any recovery often costs more than the gold is worth. The same applies to e-waste.


Duly noted thank you. I'm gonna keep close attention to time spent and money spent vs gold recovery from the black sands after I figure out if the majority is in the magnetics or non magnetics and which method is best to do further recovery of gold from it. If the costs out weigh the gold value then I'll just stock pile for now.


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## cuchugold (Nov 29, 2017)

Hi Paul. You process a lot more material than I do, but here is my process which aims to save time.

I sieve and classify, before panning, so all of of my coarse gold I grab easily. I accumulate the finer black sands portion that contains fine and very fine gold particles, and keep in a separate pile to do once a week or when the pile is big enough.

The 'traditional' way they do it around here (to recover 'the butter' i.e. the flour gold) is to apply mercury to amalgamate the gold, to finally retrieve a blob of amalgamated gold. I personally find it too time consuming.

First I apply a strong magnet several times to remove as much as possible quickly. 5-10 minutes.
Then I add a cup of 'cemented nickel' to the pan, and fill the pan with the non-mag black sands. I shake hard several times, and with a spoon and hand I discard the top of the black sands till I reach the nickel, then refill the pan with sands, and repeat. When finished with the pile, I apply the magnet again to remove the nickel, and voila the gold is left in the pan almost completely clean.
Whatever black sands I have removed I put in a big bag (1 Ton capacity), and when bag is full I fill it with a chlorine leach for a week. Which I cement, afterwards. I have not tested how much I leave behind, but it's not much, and probably not worth looking at it. But I'm leaving other valuable minerals there too.

I never thought to leach the magnetic and non-magnetic separately, but I'm going to try that idea. :G 

This 'cleanup', without the leach, takes me about an hour, at a leisure pace.


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## im1badpup1 (Nov 29, 2017)

Well it seems to catch flour gold but the tiny micron invisible unless its heaped type i think goes straight through that is until the cubes loaded with blacksand then it seems to be catching it as well.
Something to do with vortices and active matting particle exchange of denser and lighter material.
My blacksand is different to yours. Mines beachblacksand everythings well worn all my golds fine flat rounded and a bitch to catch at all. Ive a lot of elemental lead too.
Now bearing in mind leads a third of the density of gold the cube catches that stuff very well. To well maybe lol.
Theres nothing to say it wont concentrate your encapsulated gold down the density can be halved and it still work and do a good job thinking about it some more.
Its well worth to beg or borrow a goldcube and just try it and see. For time and efficiency your looking at just over an hour per ton of 1/8 or smaller material superconcentrated down to a few kilos of the densest particles. A goldcubes described best as a superconcentrator.
Ive not assayed my tailings yet but like all tools the cube wont catch 100% while running non uniform sized material but its pretty close.
Im just building a magnetic sluice like a cleangold to addon and catch a bit more rather than have to crush grind tons of material. I expect maybe half a gram or so per ton from that. The cube dont miss much. 
I like that method you do cuchu its a great idea too


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## cuchugold (Nov 30, 2017)

Someone asked about leach. There is a lot of info in this free link, for small miners:
http://webpages.charter.net/kwilliams00/bcftp/bcftp.htm

For cyanide leach, I'd refer to Deano's posts and procedures. Obviously a big operator.

Also it is worth knowing that fine particles of gold can be perceived as brown, black, or invisible by the human eye. They are there though.

edit: I'm not an expert in leaching. I suggest others to study the subject matter in depth before experimenting, and experimenting before going to the field. The soils that I deal with are acidic in nature, therefore I use a chlorine leach, that's when I ever do a leach, which is not always depending on the site, water, etc, etc, because someone told me to do that instead of cyanide, and explained why. If your soil is alkaline in nature, then cyanide will probably work better than chlorine. Cyanide also has many other advantages. If you don't want to gas yourself with cyanide or chlorine, lose the values, or both, please study and experiment first in a small scale. Good luck.

edit 2: There is also a VAST difference between leaching concentrates, and leaching ore, due to the amounts processed, and values present.


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## Reno Chris (Dec 1, 2017)

Another thing is that there is no magic to black sands. A lot of inexperienced guys get all all caught up in the mystical trapped gold in black sands, and look for some special way to recover it. However 99% percent of the time that is BS. The third most abundant element in the earth is iron. Surprise, lots of rocks contain iron minerals, because iron is so common. The iron minerals are heavy and tend to accumulate with the heavy material concentrates. Most of black sand comes from rocks with essentially no gold and the iron minerals from those rocks also have essentially no gold. A lot of times the bulk of the gold left in placer cons is smaller particles of free gold that had been missed in previous recovery - remember nothing get 100% of the gold. 
Do the testing that Deano recommended and get back with us.


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## rickzeien (Dec 17, 2017)

Bump

Sent from my LG-H872 using Tapatalk


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## cuchugold (Dec 26, 2017)

I saw one of these in Brazil. I was very impressed. From milled ore to almost completely clean gold, ready to smelt. All different densities can be recovered, re-cycled, etc.
It's probably not very hard to make a similar one.
https://www.youtube.com/watch?v=hkJxila5NY0

edit: The people in charge were getting the coltan, the magnetite, even the small garnets (about 3.7 density).


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## Palladium (Dec 26, 2017)

Now i'm a refiner and not a miner, but to me those pieces of gold sure seem to be really round after all that grinding. Anyone else with experience see that as normal?


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## cosmetal (Dec 26, 2017)

Palladium said:


> Now i'm a refiner and not a miner, but to me those pieces of gold sure seem to be really round after all that grinding. Anyone else with experience see that as normal?



I noticed the same thing.

They almost look like prills from a smelt. Was he processing just raw ore or also slag?

James


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## anachronism (Dec 26, 2017)

Reno Chris said:


> Another thing is that there is no magic to black sands. A lot of inexperienced guys get all all caught up in the mystical trapped gold in black sands, and look for some special way to recover it. However 99% percent of the time that is BS.



What Chris said. The plethora of posts this year about magical black sands is just.. magical. In a Harry Potter kind of way.


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## cuchugold (Dec 26, 2017)

I don't know about the really small round bits, because just now is when I'm really paying attention (Deano's teachings). What I have observed before, is that when you put ore in a hammer mill, the crystals get beaten and become rounded like little weathered nuggets in all sizes, some of which get trapped in the mill's sieve. So maybe the mill is "rounding" all the bits and pieces of metal while crushing the quartz matrix.


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