Gold extraction using chemicals

[Rickrofe]

I have on a patch of Quartz reef with really fine gold embedded in the rock. I have been crushing the rock then using a blue bowl to capture the fine stuff, but I am finding it just gets washed away - the gold is fine like flour? I have been thinking about using Aquaregia or sodium cyanide leeching to extract the metal. Does anyone have experience using these extraction processes? I am more interested in the Aquaregia method as cyanide is so dangerous; any guidance welcomed...

Rick

 

[Coyote]

Yeah I've had a bit of experience using Cyanide. You need activated carbon to adsorb the au from the slurry and then strip the au back out of the carbon, then electrowin the gold. dry the sludge and smelt with flux's.
Not really that easy.

I guess the other way may be to do a large bottle roll and filter the liquor and precipitate with zinc. I have never done this but from what I know it's fairly straight forward.

Cyanide is a nasty if not handle correctly and the pH need to be kept high.

Have a look on the net.

Cliff

 

[AtomRat]

Aquaregia is just as dangerous, it just wont kill you with exposure as bad as the cyanide would.
It is not recommended to try anything like this without experience on what to do. I have been using chemicals for several years now and use every safety precaution there can be.

You will need a basic chemistry setup, you can find many vids on youtube for gold refining.

I can explain the process, but its not how you can just do it, you need measurements and accuracy.

You can make aquaregia by combining Nitric Acid and Hydrochloric Acid ( HNO3+3 HCl ) which will eat most of the metals and the Au will leech into the solution. The Au is then precipitated out from the solution using the Urea process or similar with Sodium Metabisulfate Na2S2O5, Na-O-(S=O)-O-(S=O)-O-Na. The gold with then form a dark powder in the solution over time and will settle to the bottom of the flask. After that you need to clean the gold further with Hydrochloric Acid, Sulfuric Acid and then distilled water. It is then smelted from powder form into a button.

As I said, you cannot just get aquaregia and expect it to do all the work for you. There is a lot involved and it is all using dangerous chemicals that can majorly hurt you if there is a spill or accident. Even if you dont know the correct way to mix the chemicals, you could end up getting a drop of nitric acid or aquaregia in the eye. It is not something that someone should be playing with without experience!

Au + 3 HNO 3 + 4 HCl is in a favored equilibrium with [AuCl 4]() + 3 [NO2] + [H3O](+) + 2 H2O

You then also need to know how to either re-use the chemicals, or neutralize them and correct disposal of them.

Another way to do it, but leads you to exposure to another chemical and other issues is the copper + mercury plate. Covering a flat copper plate with a thin layer of mercury will give you a surface to run the slurry over and it will absorb all of the fine gold on its way over the plate. After you have ran your material, the mercury is scraped from the plate and cooked in a safe retort. Using a retort can be dangerous as well, you need to make sure no mercury fumes get extracted into the atmosphere or into your lungs. If done correctly, it is probably safer than the Cyanide and Aquaregia ways.

 

[Barra_Mad]

Yeah I agree with AtomRat I have done courses on extractive metallurgy and would not recommend it be done in you shed with all the proper safety equipment and know how. Though if the gold is visible it will be best just to stick to gravity separation in my experience blue bowls are not fool proof and cyclone type separator or shaker table will be the best way to go. These cost a lot to buy so depending on the amount of ore you have it might balance out in the end. I think Angus McKirk make a small portable shaker table that would be my first choice to do what you trying to do. check out the link below

http://www.prospectingsupplies.com....orofino-grande-shaker-table-cw-12-v-pump.aspx
http://www.prospectingsupplies.com....ining-manufacturing-orofino-shaker-table.aspx

 

[gcause]

[video=480,360]http://youtu.be/X6Sawj0HyF0[/video]

 

[rc62burke]

Hey Rick
I would forget the chemicals!!
Get the concentrates down to the least amount of quartz that you are happy with & then smelt it in a furnace with a good flux, the qtz will be converted to glass & your "Gold" will be freed in a button.
cheers
Lee
p.s I am building a furnace & will put up pics soon

 

[AtomRat]

http://youtu.be/X6Sawj0HyF0

I did forget to mention the borax method as well, yes, thank you gcause. It is probably the safest out of them all actually.

I did also find on youtube a few mobs doing chemical free electrolyte removal of gold, maybe something else to look into.

 

[Rickrofe]

Thanks all for such a comprehensive response, this forum is worth it's weight in Gold .

There appears to be a common theme running through your responses regarding safe (and best) practice when extracting gold using chemicals. I would like to learn more about courses on extractive metallurgy if any body can provide some pointers? I have a pretty good set up for the Aquaregia process method; I will give it a try and post a video on the process and the results once completed. Once again thankyou all for the excellent feedback.....

Additionally, thanks for the science lesson from AtomRat appreciate the detailed breakdown.

Cheers

Rick

 

[thedigger]

The quartz will not melt, unless,you can get the temp to over 1600 c,and that will take some doing.
In regards to using aqua regia,that can be tricky to get the system right,you may read all about it,but you can lose gold if you do not get it right.The chemicals have to be the right grade to be used for refining.
As Barra mad said a shaker table,might be you best bet,but a small might cost between $2.5 $3.0 grand,and you will need your material very fine,for fine gold in stone.

Regards The digger

 

[rc62burke]

Thanks all for such a comprehensive response, this forum is worth it's weight in Gold .

There appears to be a common theme running through your responses regarding safe (and best) practice when extracting gold using chemicals. I would like to learn more about courses on extractive metallurgy if any body can provide some pointers? I have a pretty good set up for the Aquaregia process method; I will give it a try and post a video on the process and the results once completed. Once again thankyou all for the excellent feedback.....

Additionally, thanks for the science lesson from AtomRat appreciate the detailed breakdown.

Cheers

Rick

Hey Rick
Your set up ??? will this be done indoors or outdoors??????
Indoors? do you have a fume hood? & filter? if not I would STOP NOW, the fumes given off in this process will attack ALL metal in your work area!!!!!!!!!!!!!

Digger
Everything has a melting point! high temps hmmm that's what the Furnace is for!!! the fine particles of Quartz remaining should not be too much of an issue in the furnace.
cheers
Lee

 

[Rickrofe]

You must have been reading my mind! I just purchased a ventilation system today.

As for the quartz, I am grinding the ore using a small home made ball mill, I then pan the powder (using a blue bowl) to remove most of the rubbish before dissolving in auqaregia. I ran a batch of solution I had last night and it worked really well.

Thanks for the head up....

 

[gcause]

Be careful, this is from another gold forum:

You should not boil your solution, not ever. You also shouldn't be dissolving anything indoors without a fume hood, and even then it should be totally separate from your house. You do not want to breath in the gases that this process creates. AR, as it dissolves metals, produces NOx gas, a brown rusty red looking gas that can kill you if you breath it in. This is extremely important, you might also be affecting people around you. You should only dissolve things in AR either under a fume hood, or outside in a well ventilated area, upwind from the reaction.

They recommend this book:

https://www.scribd.com/doc/2815953/Refining-Precious-Metal-Wastes-C-M-Hoke

Hope this helps.

 

[thedigger]

Well good luck with the furnace, and melting quartz,I would like to see that,I speak from a lot of experience.

Regards TheDigger

 

[rc62burke]

Well good luck with the furnace, and melting quartz,I would like to see that,I speak from a lot of experience.

Regards TheDigger

Hey Digger
My apologies! I think my post sounded a bit harsh ( that can happen in a short reply)
I have done a lot of research & some methods recommend adding a few bits of quartz or glass to the flux to get right fluid mixture? from memory.

Mate if you have experience in this field I am all ears & will soak up as much info as you are willing to share.
cheers
Lee

 

[elrodeo]

Be careful, this is from another gold forum:

You should not boil your solution, not ever. You also shouldn't be dissolving anything indoors without a fume hood, and even then it should be totally separate from your house. You do not want to breath in the gases that this process creates. AR, as it dissolves metals, produces NOx gas, a brown rusty red looking gas that can kill you if you breath it in. This is extremely important, you might also be affecting people around you. You should only dissolve things in AR either under a fume hood, or outside in a well ventilated area, upwind from the reaction.

They recommend this book:

https://www.scribd.com/doc/2815953/Refining-Precious-Metal-Wastes-C-M-Hoke

Hope this helps.

Free Downloadable version here : http://www.recyclingsecrets.com/free-reports/refining-precioius-metals-waste-cm-hoke.pdf

Some more info available on this site : http://www.goldnscrap.com/index.php/gold/86-high-karat-gold-21k-23k-refining-and-melting