# Gold frm used mining process equipment.



## Anonymous (Oct 13, 2010)

After cleaning up used james and deister tables and calcining the waste, i put the crushed fines over a half size james table and took about a pound of Au off the sweet cut. My problem is the middlings and tails. I tried aqua regia on the middlings and percipetated with sodium metabisulfite but had very poor to no recovery. The bulk of the sand is rust and the grade 100 g/t. The tails grade at 40 g/t. The AR worked perfect on the sweet cut but hits a wall on the middlings and tails. I have not tried leaching in HCl but when treated with nitric the liberated Au lays on the flask bottom. I have had the same problem with middling from an old stamp mill, the AR is deep brown red liquor but no Au percipitated with sod met. Is the excess iron dissolved perhaps a cause of the problem. I simply evapourate the AR down and add HCl befor the sod met. Please, any boffins out there who can help?


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## MiltonFu (Oct 13, 2010)

http://en.wikipedia.org/wiki/Boffin


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## 4metals (Oct 13, 2010)

You have possibly saturated your solution with iron which is causing any PGM's to precipitate. The assay you gave is roughly 1 to 2 1/2 oz/ton and not the concentration you want to be going after with aqua regia. Try investigating some leach procedures if you have this fraction in quantity. 

First off have you tested any of your solutions with stannous chloride to see if they are holding values or are you just determining it is holding if gold comes out on the metabisulfate drop? 

Give us some more details so we can give you the answers you need. 

BTW thanks Milton for looking up boffin!


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## martyn111 (Oct 13, 2010)

I hate having to correct you 4metals but shouldn't that read metabisulphITE rather than metabisulphate?


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## 4metals (Oct 13, 2010)

Yes you are correct, and no need to hate to correct me. So much for posting from the airport on a blackberry!


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## Anonymous (Oct 14, 2010)

Thankyou for the english lesson but in this neck of the woods a boffin is an expert. 

Thankyou 4metals for your time, i have about a ton of this material now and previously stripped the Au out with Kcn which was not very sucessful either but cyanide is not an option now. (Electro plated onto steelwool with the Kcn) 

The grade is estimated from 250 ml ore panned, resulting in a 75mm (3") tail. That would not account for fine Au still trapped in the grains with a d90 grind of 75 micron. 

Is thiourea a better option then? but the heamatite from the rust bothers me as its excessive. The SnCl2 simply indicates Au in the AR solution, dosnt say much more. Its dark purple on the evapouration dish. 

Hope this is enough info for you as i dont really know what more to say lol. Thankyou.


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## goldsilverpro (Oct 14, 2010)

I just moved this thread to the Mining category. In the future, please post any and all topics involving any sort of mining or mining materials in this category.


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## 4metals (Oct 14, 2010)

It is good that GSP moved this thread here, it is more likely to be noticed by members with hands on experience with different leach systems. 

I have done some ore leaching but it was in the 80's and I'm sure there are members who have used leaches which are more prevalent today than 20 years ago. 

Trying ore in aqua regia is a common mistake, most don't consider the implications of using acid on such large lots. I asked if the solution tested positive with stannous chloride only to get a relative idea of its concentration in the acid. 

When you get your metal concentrates together and are ready to produce some high grade bullion, come back to the part of the forum where the non rock guys live and we can help you. 

Good Luck


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## aussco999 (Nov 2, 2010)

Foll:

Often the middles and sometime the tails from the first shaker table are ran directly onto other tables with a different set up (slope, pitch, bump speed and water flow) that will handle the middles/tails at a slower rate, allowing for a better separation. I once ran 4 tables in series on a project and had a business associate the ran 40 tables.

To get this type of gravity recovery system to work properly it’s important to know; 1.) the initial point of precious metal liberation and 2.) the smallest economical grinding size of liberation. Between the high/low grind parameters, recovery may be improved with another screen classification. For best recovery results on the middles/tails, try a re-grind of the sands to liberate more gold. The minimum recovery limits (in real life) when using several tables is about 400 mesh (34 micron). Everything after that is mostly wishful thinking.

If you still have good values in your middles/tails (and 40/100 g/t are good numbers), then you might consider either a flotation system that can recover down to about one micron or a batch leaching system.

With a ton of your material (enough for 2 or 3 large drums), and a re-grind to the lowest liberation point, you could re-table the material or go directly to a leach. Cyanide would be my first choice, because when handled properly, it’s cheap and not effected by the high iron content in your material. Another bulk leach you might check into is thiourea, but it has it’s own set of problems. You should always think about safety first by understanding the pros and cons of each leach procedure.

An out of the box thought; in the past I have sold clean gold laden sands to a copper refinery as a fluxing ingredient and was paid for the assayed gold content. If there are any refineries nearby, you might want to check with them.

Good luck with your project, :mrgreen: 

John


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