# HCL/peroxide method and black sand



## yonderfishin

Just a few more questions if you all dont mind.


How effective would HCL/peroxide be in breaking down black sand to remove micro gold ? Does it even break down the sand ? How about pyrite ?

Until recently I thought that aqua regia was the only option chemically , but I just read a few things that said the acid/peroxide will work its just a lot slower. Does it really even break down the gold too ? 

Though time consuming , this could be a lot more affordable than aqua regia if its true.

Thanks for any help/info you can give.


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## Geo

if you roast the sands to red hot and keep it there for about a half hour, you may be able to use some ferric chloride to remove the iron. if you want to break the sand down, you will need a mill. thats a mechanical process and not chemical. black sand concentrates contain many different materials besides magnetic ferrite. theres silica's and quartz and pyrite, almost all are resistant to acid attack. milling will reduce the physical size of the material but it will not alter any of the other aspects. it will still be acid resistant but milling will release more retrievable gold from leeching.


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## yonderfishin

Geo said:


> if you roast the sands to red hot and keep it there for about a half hour, you may be able to use some ferric chloride to remove the iron. if you want to break the sand down, you will need a mill. thats a mechanical process and not chemical. black sand concentrates contain many different materials besides magnetic ferrite. theres silica's and quartz and pyrite, almost all are resistant to acid attack. milling will reduce the physical size of the material but it will not alter any of the other aspects. it will still be acid resistant but milling will release more retrievable gold from leeching.




Thanks Geo. I knew there would be things like silica and quartz left but I was figuring I could filter those out , as long as the mojority of what makes up black sand had been dissolved by the acid and the gold wound up in supension that could be precipitated out. By breaking down of the sand I just mean eaten away by the acid. Seems like the step of mechanically milling the sand could be skipped if "most" of it wound up being dissolved , is this wrong ?


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## Geo

by "most" if you mean iron, then yea, most of the iron will be removed. everything else will stay as is. you have to understand that iron will be the most troublesome element to a successful leaching process. by removing the iron, it should be somewhat easier. if you have free standing gold in the black sands, leaching will work to recover the largest portion. of coarse if its free standing gold, a gravity trap will separate most of the gold from the sand. if its ore with gold locked into the matrix, chemical leaching will have little effect. refractory ore will have sulfides as well as organic carbon, both will effectively stop the leaching process in its tracks. the roasting process will help with these two troublesome elements, but the temperature has to be high enough to reduce carbon into carbon dioxide and the sulfides and sulfates to sulfur dioxide. then mill to release the trapped gold to be leached. the leach can proceed unimpeded to completion. 

i hope this helps.


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## yonderfishin

Geo said:


> by "most" if you mean iron, then yea, most of the iron will be removed. everything else will stay as is. you have to understand that iron will be the most troublesome element to a successful leaching process. by removing the iron, it should be somewhat easier. if you have free standing gold in the black sands, leaching will work to recover the largest portion. of coarse if its free standing gold, a gravity trap will separate most of the gold from the sand. if its ore with gold locked into the matrix, chemical leaching will have little effect. refractory ore will have sulfides as well as organic carbon, both will effectively stop the leaching process in its tracks. the roasting process will help with these two troublesome elements, but the temperature has to be high enough to reduce carbon into carbon dioxide and the sulfides and sulfates to sulfur dioxide. then mill to release the trapped gold to be leached. the leach can proceed unimpeded to completion.
> 
> i hope this helps.




Yes it helps clear it up a bit. There may be some gold trapped in the other parts but I am thinking the majority of whats there is freestanding microscopic gold that cant be seen with the naked eye. Pretty much all of that would defeat any kind of gravity trap I could imagine. The stream that the concentrates come out of is literally full of fly speck to pinhead sized flakes as well as some type of pyrite ore that I have successfully melted in a small amount of with a propane torch and found visible gold inside the slag left over. The gold itself has been flattened and pulverized extensively by the glaciers that brought it here and I am thinking that if there is this much fly speck to almost pinhead sized specks throughout the stream then there "almost" has to be a huge amount of gold pulverized to microscopic size that I am not able to see , possibly many times more than the visible gold. Its a natural conclusion that the gold I can see is just the portion that was lucky enough to survive the trip somewhat still intact visibly. I could probably tell for sure if I had a microscope but I dont , yet anyway. I could further classify it down far enough that the majority if the sand is gone but that borders on ridiculous with the amount of time thats all gonna take. I think I will start trying to piece together a ball mill of some sort to grind up the concentrates , thats gonna be the only realistic way to break down all the larger pyrite type ore anyway. Thanks for your help.


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## solarsmith

pyrite ore? use a gravity system to remove the free gold then you can try copper sulfate as a conditioner and a xanthate to float it with mibc as a frother. floatation works best on very small ore (150 mesh) and sulphide ores. it will also float all the lighter pgms as well . there are 100s of ways to concentrate ore. concentrating ore should be done when ever it can be done.
then roast, then mill ,then leach , rinse and reapeat. Just my 2 cents.
thanks Bryan in Denver colorado


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## urbanminer

What is the most common size of your gold? -100 to +150 mesh? -150 to + 200? Smaller? Without knowing what your dealing with you cannot move forward. At some point dealing with micron gold is not cost efficient. Classify your samples as closely as you can and pan. Record your findings. Yes, -300 mesh can be panned. I've done it and hate it, but it can be done with decent results. 

Let's look from another perspective. Cost efficiencey. Let's assume there is 10 grams a cubic yard. Method A: I can move 2 cubic yards a day with 60% recovery and only 1 gram going to opperating costs. I net 11 grams for the day. Method B cost twice as much to opperate with 80% recovery, but can only move half the material. Now I'm netting only 6 grams a day. Method C is 90% efficient. It costs double again and the material is halved, too. Of the 5 grams possible, I get 4, but it cost me 4 grams to get. I'm broke!

Py point is that sometimes trying to get ALL of the gold may not be worth your time. If your asking the question purely for the knowledge, I'm sitting on the edge of my seat wanting to find the same answer. Until then, I'll be happy with my 60% dredging opperation this weekend.


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## Traveller11

yonderfishin said:


> Just a few more questions if you all dont mind.
> 
> 
> How effective would HCL/peroxide be in breaking down black sand to remove micro gold ? Does it even break down the sand ? How about pyrite ?
> 
> Until recently I thought that aqua regia was the only option chemically , but I just read a few things that said the acid/peroxide will work its just a lot slower. Does it really even break down the gold too ?
> 
> Though time consuming , this could be a lot more affordable than aqua regia if its true.
> 
> Thanks for any help/info you can give.




Lazersteve clearly states that the acid/peroxide is NOT the method to use to remove iron in the form of black sand from placer concentrate. However, he does not tell us what the preferred method of removing black sand would be.

Unlike other magnets, N52 grade neodymium rare earth magnets will pick up haematite as well as magnetite. The problem with magnets is that tiny particles of gold will get "entrained" by a wave of black sand and become lost as the magnets draw the black sand from your concentrate. It is far from a perfect method but, if black sand is placed in a pan of water and a source of vibration added (orbital sander duct taped to the bottom of the pan), one can remove up to 90% of the iron black sand if one is careful. The vibrations should settle the gold particles to the bottom of the pan. The N52 magnets should be attached in a line to a bar that can be passed over the pan at a uniform height. This height should be just low enough to pick up black sand and leave a thin layer of black sand on the bottom of the pan.

However, we are still left with enough iron black sand to wreak havoc with most leaching methods, in particular, the acid/clorox leach.


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## yonderfishin

urbanminer said:


> What is the most common size of your gold? -100 to +150 mesh? -150 to + 200? Smaller? Without knowing what your dealing with you cannot move forward. At some point dealing with micron gold is not cost efficient. Classify your samples as closely as you can and pan. Record your findings. Yes, -300 mesh can be panned. I've done it and hate it, but it can be done with decent results.
> 
> Let's look from another perspective. Cost efficiencey. Let's assume there is 10 grams a cubic yard. Method A: I can move 2 cubic yards a day with 60% recovery and only 1 gram going to opperating costs. I net 11 grams for the day. Method B cost twice as much to opperate with 80% recovery, but can only move half the material. Now I'm netting only 6 grams a day. Method C is 90% efficient. It costs double again and the material is halved, too. Of the 5 grams possible, I get 4, but it cost me 4 grams to get. I'm broke!
> 
> Py point is that sometimes trying to get ALL of the gold may not be worth your time. If your asking the question purely for the knowledge, I'm sitting on the edge of my seat wanting to find the same answer. Until then, I'll be happy with my 60% dredging opperation this weekend.




I am not familiar with mesh sizes , still new at this. The most common visible gold I have is fly speck to slightly larger , almost pinhead size and super thin.....if that means anything , and I am seeing some that is so small that if I take my eye off it for a second its impossible to locate again in the pan. But placer gold left behind in glacial debris might be different than what many folks deal with in that its been literally pulverized nearly out of existence and I am thinking there should be a lot of it that is truly microscopic , not even visible to the naked eye. If there is plenty that is visible then there should be plenty of it around that cant even be seen without a microscope , possibly MUCH more of it than the visible stuff. I know its not cost efficient to go after , but since I see it as a fun hobby I dont mind spending just a little to see if my theory is correct , as long as I dont spend too much.


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## Traveller11

yonderfishin said:


> urbanminer said:
> 
> 
> 
> What is the most common size of your gold? -100 to +150 mesh? -150 to + 200? Smaller? Without knowing what your dealing with you cannot move forward. At some point dealing with micron gold is not cost efficient. Classify your samples as closely as you can and pan. Record your findings. Yes, -300 mesh can be panned. I've done it and hate it, but it can be done with decent results.
> 
> Let's look from another perspective. Cost efficiencey. Let's assume there is 10 grams a cubic yard. Method A: I can move 2 cubic yards a day with 60% recovery and only 1 gram going to opperating costs. I net 11 grams for the day. Method B cost twice as much to opperate with 80% recovery, but can only move half the material. Now I'm netting only 6 grams a day. Method C is 90% efficient. It costs double again and the material is halved, too. Of the 5 grams possible, I get 4, but it cost me 4 grams to get. I'm broke!
> 
> Py point is that sometimes trying to get ALL of the gold may not be worth your time. If your asking the question purely for the knowledge, I'm sitting on the edge of my seat wanting to find the same answer. Until then, I'll be happy with my 60% dredging opperation this weekend.
> 
> 
> 
> 
> 
> 
> I am not familiar with mesh sizes , still new at this. The most common visible gold I have is fly speck to slightly larger , almost pinhead size and super thin.....if that means anything , and I am seeing some that is so small that if I take my eye off it for a second its impossible to locate again in the pan. But placer gold left behind in glacial debris might be different than what many folks deal with in that its been literally pulverized nearly out of existence and I am thinking there should be a lot of it that is truly microscopic , not even visible to the naked eye. If there is plenty that is visible then there should be plenty of it around that cant even be seen without a microscope , possibly MUCH more of it than the visible stuff. I know its not cost efficient to go after , but since I see it as a fun hobby I dont mind spending just a little to see if my theory is correct , as long as I dont spend too much.
Click to expand...



You are on the right track looking for a chemical leaching solution to recovering microscopic gold. Many people talk about gravity methods and panning -200 to -300 mesh gold (mesh refers to the number of openings in a piece of screen one inch long. 300 mesh would be 300 x 300 or 90,000 openings in a one inch square piece of screen) but just ask them how many ounces they recovered last year panning 200-300 mesh gold. Or, better yet, how they classified their material down to that size prior to panning. The kindest word I can find for this notion is "impractical".


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## urbanminer

It is impractical on a large scale, but on a small scale, you can learn what size of gold you have and use that to determine the best recovery method. To me, it is even more impractical to go blindly into the use of chemicals without studying what you have. What proof do you have that there is any appeciable amount of micron gold?


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## yonderfishin

That would be the reason for an assay.


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## Traveller11

urbanminer said:


> It is impractical on a large scale, but on a small scale, you can learn what size of gold you have and use that to determine the best recovery method. To me, it is even more impractical to go blindly into the use of chemicals without studying what you have. What proof do you have that there is any appeciable amount of micron gold?




Do you think for one second that I am just guessing at the values in the material I am working with and the particle size of the PM's in that material? 

I am asking for assistance in removing black sand from my concentrates by a chemical method, as is the fellow who began this thread. If you do not know the answer, then there is not really much you can tell us.


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## Geo

if you want to remove the iron, add ferric chloride. it will dissolve the iron. the solution will be red starting out and turn black when saturated.

you really should heat the sand first. i used a cast iron dutch oven with a lid. a good hot wood fire with enough fuel to bring the cast iron to red hot will work.


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## Traveller11

I'll give it a try. What does the iron, in the form of the oxides haematite and magnetite, become after you add ferric chloride to it? Aren't you simply adding more iron? Do you filter iron in solution after you add it?

Also, what kind of fumes are released by adding frric chloride?


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## Geo

when you roast the sand, it will emit sulfur dioxide gas and carbon dioxide gas. this is from any sulfides or organic carbon. this leaves you with a clean mix of minerals to work with. the ferric chloride solution will digest any free iron, you could use hcl but the ferric chloride works faster on iron. diluted sulfuric acid also removes iron, but i think it works better on iron oxide. as the iron is dissolved, hydrogen gas is emitted but not enough to be dangerous in a ventilated space. its the same principle as AP but your using iron instead of copper. adding O2 does not help in this process, but heat does. after the solution is either saturated or there is no more iron to dissolve, the solution can be rinsed out of the sand.you should be able to get a good leach out of the material. its always a good idea to know what you are working with, so before you start the leaching process make sure you have gold in the material. too, theres almost always a percentage of silver where you find gold, so choose a process to leach that will minimize any problems with silver chloride if its a problem for you. if not, AR or hcl/Cl should work fine.


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## Traveller11

Geo said:


> when you roast the sand, it will emit sulfur dioxide gas and carbon dioxide gas. this is from any sulfides or organic carbon. this leaves you with a clean mix of minerals to work with. the ferric chloride solution will digest any free iron, you could use hcl but the ferric chloride works faster on iron. diluted sulfuric acid also removes iron, but i think it works better on iron oxide. as the iron is dissolved, hydrogen gas is emitted but not enough to be dangerous in a ventilated space. its the same principle as AP but your using iron instead of copper. adding O2 does not help in this process, but heat does. after the solution is either saturated or there is no more iron to dissolve, the solution can be rinsed out of the sand.you should be able to get a good leach out of the material. its always a good idea to know what you are working with, so before you start the leaching process make sure you have gold in the material. too, theres almost always a percentage of silver where you find gold, so choose a process to leach that will minimize any problems with silver chloride if its a problem for you. if not, AR or hcl/Cl should work fine.




Hot damn, Geo, I do believe you have the answer!

I was sceptical at first, not quite following how adding iron could remove iron into solution, until I came across an article last night about the production of ferric chloride from scrap iron and surplus chlorine gas. They supplied the following formula:

2 FeCl3 + Fe = 3 FeCl2 or, in English, 3 Ferric Chloride + Iron = 3 Ferrous Chloride

After this, they bubble chlorine gas through the ferrous chloride solution and end up with a larger amount of ferric chloride or:

3 FeCl2 + 1.5 Cl2 = 3 FeCl3

I hope ferric chloride will work at removing the oxides magnetite and haematite from my material although, as you said, there is always dilute sulphuric acid for oxides of iron. From what I've read, though, ferric oxide seems marginally safer to work with.

I can't seem to find much information on the disposal of ferrous chloride (unless I find a chlorine generator and make ferric chloride) though, from what I've read, this is a major problem for the steel industry. One article said that, by adding sodium carbonate to it until a ph of 7-8 is achieved will cause the iron to precipitate and neutralize the solution. Does this sound right to you?

P.S. If this works, I'll name the first ounce after you. :mrgreen:


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## Traveller11

I think I'd better add a note to any layman, such as myself, who happens to be looking for the same solution to the black sand problem, it is a good idea to invest in acid proof gloves, apron and a good face shield and to do all of this outdoors. 

I also recommend pulling up the MSDS on both ferric chloride and the end product, ferrous chloride.


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## yonderfishin

Traveller11 said:


> I think I'd better add a note to any layman, such as myself, who happens to be looking for the same solution to the black sand problem, it is a good idea to invest in acid proof gloves, apron and a good face shield and to do all of this outdoors.
> 
> I also recommend pulling up the MSDS on both ferric chloride and the end product, ferrous chloride.





It never hurts to mention using safety precautions. Not using them could hurt pretty bad.


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## yonderfishin

Sounds like a good idea , where do you get ferric chloride ?


I am in the process of building a little smelting furnace. Rather than going full out chemical extraction Im thinking if I reduce volume and get rid of most of the iron the smelting process will be all that much easier.


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## Geo

if your not comfortable making your own ferric chloride, it can be bought at chemical supply places and small quantities (a quart or pint at a time) can be bought at radioshack.


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## Traveller11

Geo said:


> if your not comfortable making your own ferric chloride, it can be bought at chemical supply places and small quantities (a quart or pint at a time) can be bought at radioshack.



Hi Geo

What is the method for making ferric chloride? I've been checking into buying it and it seems that, although it is not overly difficult to purchase in Canada, shipping it to a remote northern location, such as mine, is a bit tricky.


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## Traveller11

I think I will be able to answer my own question. Here is something I found:

http://doityourselfchristmas.com/forums/showthread.php?7954-Here-s-how-I-make-ferric-chloride-etchant


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## Traveller11

Okay, going back over these instructions, I think I've done something here that skipped a step in the process.

In the instructions, the author tells us to place steel wool pads into muriatic acid, making ferrous (not ferric) chloride (FeCl2) as Step 1 in the ferric chloride (FeCl3) making process. He describes ferrous chloride as a milky white mixture.

He then adds hydrogen peroxide (H2O2) in tiny amounts (please read the directions before trying this as it is dangerous). The hydrogen peroxide breaks the chlorine away from the remaining muriatic acid (HCl) and the free chlorine combines with the ferrous chloride to make ferric chloride. He describes the ferric chloride as a dark clear amber mixture resembling flat cola.

Now, remember how I said black sand is mostly the two oxides of iron, magnetite (Fe3O4) and haematite (Fe2O3)? Well, I have a plastic dish here into which I put .5 inch of black sand and then covered it with muriatic acid.

I should have a milky white mixture (ferrous chloride) but, what I have resembles his description of ferric chloride. Is it possible that the two oxides, when broken down by the acid, supplied the source of oxygen that was supplied by the hydrogen peroxide in the author's instructions? In other words, am I making ferric chloride directly by dissolving the two oxides of iron in HCl?


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## Geo

in my experience, one oxidizer is as good as another for some things. i would first try bubbling air through it with a fish tank bubbler. thats what i do and it seems to work just fine. i see no problem with steel wool, it would probably be quicker than what i use (transformer laminates) but i have nothing but time.H2O2 is just water with an extra oxygen atom. 

if the solution is red and acidic, i would bet on ferric chloride.


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## Traveller11

Geo said:


> in my experience, one oxidizer is as good as another for some things. i would first try bubbling air through it with a fish tank bubbler. thats what i do and it seems to work just fine. i see no problem with steel wool, it would probably be quicker than what i use (transformer laminates) but i have nothing but time.H2O2 is just water with an extra oxygen atom.
> 
> if the solution is red and acidic, i would bet on ferric chloride.




There is something else I am wondering about. As the material I am working with is from black sand deposits deposited by the ocean during winter storms, there is a fair amount of salt in it. While I am trying to remove the black sands, will the salt (NaCl) act as a source of chlorine and cause the leach to absorb gold as well, similar to the acid/clorox process, and cause gold to be lost with the iron removal process? If there is gold in the ferric chloride solution, can it be precipitated separately?

I know, from reading material here, that removing copper from printed circuits with the acid/peroxide method will inadvertently put gold into solution, if there is chlorine present in the AP from an unknown source.


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## Geo

there has to be a catalyst involved to break chlorine from the salt and involves electricity usually. if its a concern to you, NaCl is readily soluble in water. give it a good boil in water and rinse before you do anything else to remove the salt


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## yonderfishin

After soaking a small amount of concentrates in bleach and peroxode a few gold flakes have had a black coating taken off them and chunks of pyrite that has some black , brown , or red coating are now a shiny gold color , but it dont seem to be having much effect on most of the black sand.


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## Iron

yonderfishin said:


> Sounds like a good idea , where do you get ferric chloride ?
> 
> 
> I am in the process of building a little smelting furnace. Rather than going full out chemical extraction Im thinking if I reduce volume and get rid of most of the iron the smelting process will be all that much easier.



Hi,
I am new on this forum, I would love to know when you successfully build your furnace and get rid of the iron, as I have same issue to deal with.
Thanks


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## NoIdea

Traveller11 said:


> I can't seem to find much information on the disposal of ferrous chloride......... :



Hi Traveller11 - I have the same problem, im going to distill the ferrous/ferric chloride which produces HCl gas, which loves water and will be readily absorbed, and of course iron oxides of various forms left in the reaction vessel.

I read mention of meshes, the ones i use come out of television/computer CRT's, not sure what mesh size, butt it's small, and i see alot of small shinny gold spects.

Cheers

Deano


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## Traveller11




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## BAMGOLD

What stops the ferrous metal from sticking to the magnet all the time?


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## Traveller11

The magnet is stationary inside the drum. The ferrous material never actually touches the magnet, just the drum. As the drum turns past the point where the magnet ends, the ferrous material falls off the drum.


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## Geo

i have a question. what force moves the non-magnet material up and over the edge of the lip?


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## Traveller11

Look at the bottom of the diagram where it says "Non-Magnetic Discharge". The non-magnetics are discharged at the bottom.

Here is a photo of another magnetic separator and the link to the site. It has N52 neodymium magnets inside one of the conveyor rollers. The black sands are carried up and onto the conveyor.






http://www.goldfieldeng.com/wet-magnetic-shot-separator.aspx

A few more views of the conveyor belt system can be seen on this page.

http://www.goldfieldeng.com/


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## BAMGOLD

Traveller11 said:


> The magnet is stationary inside the drum. The ferrous material never actually touches the magnet, just the drum. As the drum turns past the point where the magnet ends, the ferrous material falls off the drum.




I understand that, but gravity will make the metal fall down, which is where the magnet is located, leading to a cycling action until it overloads and some just falls off... is that how it works, or is there other things at play here that I'm not seeing?


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## john_paok

Geo said:


> by "most" if you mean iron, then yea, most of the iron will be removed. everything else will stay as is. you have to understand that iron will be the most troublesome element to a successful leaching process. by removing the iron, it should be somewhat easier. if you have free standing gold in the black sands, leaching will work to recover the largest portion. of coarse if its free standing gold, a gravity trap will separate most of the gold from the sand. if its ore with gold locked into the matrix, chemical leaching will have little effect. refractory ore will have sulfides as well as organic carbon, both will effectively stop the leaching process in its tracks. the roasting process will help with these two troublesome elements, but the temperature has to be high enough to reduce carbon into carbon dioxide and the sulfides and sulfates to sulfur dioxide. then mill to release the trapped gold to be leached. the leach can proceed unimpeded to completion.
> 
> i hope this helps.




There not a way to melt sand by chemical?


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## jimdoc

john_paok said:


> There not a way to melt sand by chemical?



That would not be melting, it would be dissolving. 

Jim


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## butcher

john_paok,
I do not understand why you would want to dissolve the sand with chemicals, when you could dissolve metals from sand, (but even easier just to pan out the gold). 

If you have black sand it can complicate leaching, as these iron compounds do not break down easily, and the iron can complicate matters if it is not leached out, before attempting to leach the valuable metals,and leaching volumes of base metals can use up a lot of acids, it should be ground up to fine talcum powder consistency,then roasting it to cherry red hot in air, or oxygen, this can help to eliminate some sulfur compounds, this will not convert the iron oxides to elemental metal, the iron could be reduced to metal with a reducer like charcoal and lime at very high heat, then you could leach out base metals.

All of this just sounds like a waste of time to me, (pan the gold), smelting concentrates is another option but then again you could burn up more money in fuel than you may recover gold, and here again you would need to gravity separate the majority of gold from the non-gold sands in order to get the gold in concentrated enough in order to make smelting an option.

Gravity separation, is the way to go, easier and it works, that is why it is used as the method for recovering gold from sands, leave leaching for recovering gold locked up in ore (and then only use it if it is cost effective to recover the gold with this method). 

There is an acid that can etch glass but it is so hazardous we normally do not give advice or promote its use, (I have not seen a reason to use it yet in recovery or refining).

I think you are trying to find a hard way to deal with an easy material to handle.


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