Small scale gold recovery system idea

[arizau]

A while back I posted the link shown below on how to recover gold from difficult black sand concentrates developed by a Canadian research firm using funds from a government grant. The way it is presented is way above the needs and means of the average prospector on this site but I was recently made mindful of a way to scale it down for possible usage by us. Rather than use a small cement mixer to power the rod mill, why not power it with a lathe or a combo mill? It would not be too hard, and for a few bucks or from what you have on hand, to make the chamber out of a reasonably small section of pipe, load it with varying diameters of steel rod stock and let it rip. One key thing you have to keep in mind is the necessary rpm, based on the inside diameter of the chamber, required to operate efficiently. The formula on how to determine that is in the link.

This is a proven method. The method will not degrade the gold, eg. reduce the size, but will mostly flatten it usually to a mesh size larger than it originally was while, at the same time, pulverizing the brittle black sand. At this point, with proper screening, most gold is easily recovered from the surface of the screen and/or the remaining black sands can be rerun and classified through smaller screens.

Some will ask or suggest, "Why not use steel balls?" A ball mill would have a tendency to not only flatten the gold but also mostly degrade/reduce it's size thus negating the desired results which is to make the gold larger than the average size of the pulverized black sand so it can be recovered by screening.

http://www.geology.gov.yk.ca/pdf/141114_Nov1014_Grinding_for_Gold_Presentation.pdf

Maybe this will inspire someone to give it a try.

All those in favor of screening vs. blue bowl or miller table say aye.

Good luck and let us know.

 

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[Disfunctional]

I posted these links elsewhere in relation to sulfides, but thought they belonged here too.
They seem to belong together if a person is encountering sulfides. Both are eco friendly and effective at getting the job done.

GPEX ARCHIVE
Roasting Black Sand Concentrates
Roasting black sand to extract fine gold?
See post by mrscience, but you might want to read all of both these forum topics and download the pdf file mentioned in the second thread topic on rod mills.

Gpex Forum:
More detailed use of a Rod Mill
Yukon_Innovation_Increases_Gold _Recovery_for_Placer_Miners


Good luck!

 

[Bonaro]

I agree with your theory about rod vs ball mills, screening vs blue bowl.
However, while your idea would certainly work...why would I wear out my expensive precision lathe just to spare my cheap and durable cement mixer to crush rock?
I consider myself a rational man and this is well outside of my ability to justify.
Considering that 75% of us own a cement mixer and maybe 2% of us own a lathe ...do you seriously consider this to be a practical approach?

 

[arizau]

I agree with your theory about rod vs ball mills, screening vs blue bowl.
However, while your idea would certainly work...why would I wear out my expensive precision lathe just to spare my cheap and durable cement mixer to crush rock?
I consider myself a rational man and this is well outside of my ability to justify.
Considering that 75% of us own a cement mixer and maybe 2% of us own a lathe ...do you seriously consider this to be a practical approach?

Practical? Yes if you have the needs and the means to go full scale as in the Canadian presentation. For scaled down as I proposed, I don't know. I proposed this as an experiment as I said "Maybe this will inspire someone to give it a try."

Justify? Cheap or scrap material for the build so Yes. If it doesn't work then little lost.

Your reference to wearing out a lathe. There probably will be some induced vibration with such a set up. I don't know how much if any influence the side pressure (eccentricity) induced by centrifugal force would have on bearing wear which is where precision comes into play and there is tailstock support. If the bearings are already bad it would make it worse but again will such an application cause excess wear? I kind of envisioned a 3" id pipe 4 to 6" long. Maybe even ABS would work. I guesstimate the total weight to be maybe 4 to 8 lbs. including the rods and the black sand charge. I roughly calculated the RPM to be about 160. If that were to work then test with longer and/or larger pipe as a means to increase the potential of overall practicality for usage.

The above paragraph leads me to another thought! An alternative to a lathe or combo mill could be to attach to a bench mounted small motor with sheaves, rheostat or whatever to set proper revolutions. Or better yet it could be powered by rollers just like some of the big ball mills. Probably more people have old motors sitting around than cement mixers.

Cement mixer instead? Yep. If you want to build a full scale portable unit. The modification looks pretty permanent though. See above instead for shop use.

Rock crusher? Nope. Disposable grinding mill for minus 30 mesh.

That all said, you have some valid points or potential concerns.

PS: There is a guy over on the GPEX forum who says he is going to try this idea out so maybe no one here needs to be the Guinea Pig.

 

[Bonaro]

I have done a bit of ball and rod milling. It is a violent, noisy and messy task. I do agree that a lathe would actually perform this work but in the same way I am sure you could agree that your wife's finest sewing shears would trim the shrubs outside in dandy fashion. Point is, I would not put my costly lathe through this for for the pennies in gold you will likely recover. Aside from the impact and vibration, the likelihood of spilling a load of grit on the lathe would be far reason enough for me.

Why not use a much more suitable tool like a drill motor turning a pipe rolling on roller skate wheels or better yet get yourself a big rock tumbler? They are made for this type of thing.
I made a amalgamation tumbler out of a 5 gallon bucket turned by a pellet stove feed motor, cost me $0