Clean up!

[Joe S (AK)]

JED -

That always reminds me of something said to me by a sales manager a long, long time ago: "A percentage of something is usually much better than no percentage of it".

[Micropedes1]

When mine goes across my table for the second time, most everything 100 mesh and larger has been removed. At that point the remaining black sands get dumped on a leach pad. When there is a sufficient quantity of material, I turn on the pumps. Only after this extraction step do the cons get dumped.

Depending upon the skill feeding the table, sometimes chemical extraction hardly pays for the chemicals though.

[Geowizard]

Glen,

Can you selectively leach the GOLD?

- Geowizard

[Micropedes1]

Yes, to a degree. But I usually don't go to that much trouble. It takes too much gloxime (which is expensive) and is temperature dependent (hard to keep lixivant near freezing). Not sure of the reaction mechanism on this as gloxime is generally used for nickel and palladium extraction. But I suspect that the gloxime serves as a complexing agent aiding the drag-out of gold as an incidental.

If dealing with oxide....Ordinarily, I would recirculate 5-8% sodium cyanide solution along with enough caustic soda to bring the pH up to more than 10. Then supplement with ammonium hydroxide to minimize absorption of copper and minimize loss of cyanide. (A version of the Hunt process) But there is always going to be some copper drag-out to deal with later. Silver too. By the way, all these solutions are mixed prior to adding to the leach pad. Gold (and other metals) are adsorbed onto an activated carbon column. The column is stripped using concentrated caustic, neutralized, and reduced using conventional methods. If I am really energetic, I will thoroughly rinse the AC, acid wash in a CLOSED vent hood with HCl (hydrogen cyanide), and gently ash the entire column. Then digest it all with aqua regia and selectively precipitate depending upon what shows with stannous chloride test.

Sulfide is a whole different process.

The whole process is complicated. And dangerous. And takes the better part of a week just to monitor it all and keep the pH just right. It is not something that the average miner needs to mess with.

[Micropedes1]

I tried using a glycine/cyanide/peroxide lixivant on a small batch. Extraction was relatively straightforward, with minimal copper drag-out due to glycine/copper complexing. CIP adsorption as above completed it. Looks like I may be switching processes in the future.

As a side note, this does not seem to work well with ores containing appreciable amount of clay. It seems that the aluminum complexes with the glycine more readily than the copper. Ain't chemistry fun!!

[Geowizard]

Complex chemistry;

Chemistry for purposes of cleanup has to be a simple, practical part of the process. It becomes a mute issue if a typical placer operation can't do it.

The application for "leaching" normally resides in a limited realm of the mining world where the mineralogy is within certain parameters and the rock matrix is permeable. It's a GOLD in hard rock recovery process.

Cleanup of fine placer GOLD concentrates;

Amalgamation and flotation are recognized as two methods used for recovery of fine GOLD when particle sizes are getting down to 100 mesh and smaller. Simple chemistry is used.

Stay tuned, there's more!

- Geowizard

[Jim_Alaska]

Just a friendly reminder to all. Given the direction this thread is going I thought it prudent to remind folks, especially new members, that once the threads miigrate into the realm of Hg, or as it is commonly called, Mercury, I will start deleting posts. Most older members know my position and experience with Hg. The subject is a no no on these forums.

[Geowizard]

They use "it" at Nome;

"It" was used by old timers. They use "it" for fine GOLD recovery at Nome even today!

I was asked by a visitor, if I had seen a large copper plate 4 ft x 4 ft that was once used at Ophir.

No fine GOLD recovery is complete without "it".

- Geowizard

[Jim_Alaska]

Yes, they did use it. But we won't even mention it on this forum. As a matter of fact, "it" is very close to being "in the realm",

[Micropedes1]

I understand Jim’s position completely. He was trained to handle it and was fortunate enough not to end up “mad as a hatter”.

Same thing goes for hazardous chemicals. If you lack the training, you need to avoid them at all costs. One little mishap can cost your life.