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Shoutingtoe

New member
Joined
Apr 27, 2018
Messages
4
Hello, I am new to refining but I have been studying for a long time to get started. My project is to start with sluice concentrates sourced from an underground gold vein rich with gold and silver but mixed with pyrite. I started by mechanical separation with a blue bowl set up. this yields gold mixed with pyrite. I take this pyrite/gold mixture and roast at 1,000 degrees F for about an hour. Then I take the roasted material and smelt it with hank chapman flux + thinner and pour into a conical mold. At the tip of the cone I get what appears to be a gold/silver alloy that is slightly brittle. Next I take this metal cone, melt and pour into water to form shot. I take the shot and dissolve with nitric acid. (This is where my problems started) For the first run it seemed to be going well until I decided to crush the remaining slag and add to the reaction in an attempt to recover any remaining pm that didn't collect in the smelting process. This resulted in a thick gelatinous formation that pretty much stopped the reaction(my best guess is something to do with the silica in the flux). I attempted to thin this the gelatin with water and recover the remaining shot with a spoon. I then rinsed the recovered shot and started it in a separate nitric reaction. After the reaction died down I filtered out the remaining solids assuming it was mostly gold. I then incinerated the filter paper containing the solids and poured pre-mixed AR over them. I got an active reaction with red fumes. Once this reaction died down I added urea to neutralize the remaining nitric (I know now that I should have added the nitric to the HCL as needed to prevent excess nitric in the mix). When I added urea to the AR it just sank to the bottom and took a while to dissolve. I expected a head of foam as it reacted with the nitric like some videos I have seen but this did not happen. A stannous Chloride test was negative for gold in the solution but I assumed that I made the test solution wrong as I have no means to test it with a known gold containing solution at this time. I then filtered through several passes and then added sodium bisulfite and it just clumped up and collected on the bottom of the beaker. No foam or anything. I added a little heat (it was about 60 degrees outside) and it dissolved with stirring but dropped no gold. I am stumped at this point. I don't know where my gold is hiding. My next move is to make fresh stannous chloride and dissolve about 0.5g of 18k gold I have sitting around in AR then test the stannous solution to confirm it works. Then I plan to test all my solutions to see if I have gold in any of them. If this doesn't work the only place I can figure it may be is in a filter paper or in the thick gel/nitric mess holding the undissolved flux that I spooned out the remaining shot pieces from. I will definitely not be adding the crushed flux to the next batch!

Sorry this is so long but I tried to be as thorough as possible. Any suggestions as to where I went wrong or what I should try would be greatly appreciated. Thank you for your time. Also I have a concern that I may have accidentally created an explosive with the nitric acid and the gel that formed. Any thoughts on that?
 
Welcome to the forum.
I will ask the question that most will ask, how do you know that your ore is rich in gold and silver?
If you haven’t had an assay done then perhaps your just hoping it’s rich in gold and silver and the reason you did not precipitate any gold was because there was none there to start with.
 
Thank you for the reply, I have had samples assayed with positive results for both gold and silver. Also, I have recovered gold with natural purity of about 18k by mechanical means from the same source. For this particular sample gold was obvious in the blue bowl processing, I was expecting somewhere between 1 to 2 troy ounces. (I am experienced with the difference between pyrite and real gold)
 
First thing I noted is that your metal after smelting was brittle. How brittle? Easy to crush into a powder or cracking but somewhat malleable?

I have no clue where any possible gold can be, but in the end when you added SMB to the solution it just dropped to the bottom tells me that your solution was close to neutral with very little acid left. SMB needs some HCl to be present to release the SO2 that reduce the gold back into metal.

If you have any solutions left you could always put a piece of clean copper in it, any precious metals will cement out on the surface of the copper as a black powder or crust.

If you had the ore assayed, what did the report say?

Göran
 
To test your stannous requires very little gold, you say you recovered some that was around 18k just use a small amount of that to dissolve in AR to give you a test solution, without the ability to test you are just guessing what’s going on and where your gold might be.
Refining ores is rarely simple due to the mix of elements that can be present and can interfere with recovery, if you have an assay did you ask for a full breakdown of the ore as this might help explain what the problem might be.
Several thoughts have passed through my mind such as if your values are low in concentration then perhaps you need a collector metal in your smelt, also did everything dissolve from all your acid processes, no sludge or pieces left in beakers or filter papers.
 
Thank you Goran. The metal from the smelting was slightly malleable but would chip. I hit it with a hammer and the tip mushroomed with chips around the edges. I will try adding some HCL to the solution to activate the sodium bisulfite. If that doesn't work, I'll suspend some copper pipe and try to cement it out. Thank you for the help.
 
nickvc said:
To test your stannous requires very little gold, you say you recovered some that was around 18k just use a small amount of that to dissolve in AR to give you a test solution, without the ability to test you are just guessing what’s going on and where your gold might be.
Refining ores is rarely simple due to the mix of elements that can be present and can interfere with recovery, if you have an assay did you ask for a full breakdown of the ore as this might help explain what the problem might be.
Several thoughts have passed through my mind such as if your values are low in concentration then perhaps you need a collector metal in your smelt, also did everything dissolve from all your acid processes, no sludge or pieces left in beakers or filter papers.


Thank you nickvc, I plan on testing my test solution today by doing just that. My earlier assay report was not a full spectrum but I have another sample for assaying coming in the next few weeks. I will get a full report to try to identify any problem materials present. I did have some sludge and pieces of material (most of the pieces resembled blue rocks after sitting in the acid) left over in both the nitric and AR beakers. I still have everything as I never discard anything unless I am certain it has no PM. I was thinking of incarcerating the leftovers/filters and starting over at mechanical separation.
 
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