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Wis49er
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Re: Gravity concentrator versus Wave table ( 18:55:19 WedSep 20 2017 )

When I started this thread I have some real questions on the best recovery for small gold. The replies and additional comments have been excellent. Sometimes you just have to see the equipment work. So I took 5 buckets of rock to Mount Baker Mining in Bellingham WA. The wave table does not offer a clear view of the gold while working because there is lead and other metals in the ore and the gold is so small a hand lense is needed to see it. There are no locations where I could do this same test with a Falcon, ICON or knudsen bowl that I am aware of. For me the simpler the equipment the better. Another experienced hardrock miner told me there have been failures with the Knudsen bowls and Jim gave an excellent example of how that could be. I know have a better idea that a wave table might be the best option for me. Thank you all for your comments.

  
geowizard
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Re: Gravity concentrator versus Wave table ( 01:20:58 ThuSep 28 2017 )

The point is;

The process of separation of GOLD from other materials requires screening. CLASSIFICATION of particles to get equal particle size and unequal MASS is the key to success.

If you mix fine gold with Lead or Galena, SCREENING is of the greatest importance. The decision of using one method or another is of secondary interest. The methods all rely on the ability of equal sized particles having different MASS to be separated.

- Geowizard

  
geowizard
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Re: Gravity concentrator versus Wave table ( 01:27:10 ThuSep 28 2017 )

A GOLD pan;

Out of curiosity, I took a small scoop of Brue Bowl tailings screened to 12 mesh and panned them.

NO GOLD.

I took the same sample and screened it to 20 mesh. I panned the 20 mesh.

The pan had a nice GOLD smile of FINE GOLD.

The fine GOLD could not be recovered in the presence of 12 mesh heavies.

- Geowizard

  
geowizard
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Re: Gravity concentrator versus Wave table ( 01:38:17 ThuSep 28 2017 )

What's next?

Take the 20 mesh tails and screen with a 40 mesh screen.

Pan the 40 mesh.

There's the 40 mesh GOLD!

Eventually, you get down to the 100 mesh GOLD.

This process of successive classification is mandatory for fine GOLD recovery.

- Geowizard

  
Jim_Alaska
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Re: Gravity concentrator versus Wave table ( 13:13:27 ThuSep 28 2017 )

I have long been an advocate of diminishing classification. I bought a full set of small finishing screens for just this purpose.

For small endeavors such as my mining, I have found that you can really get a sense of what classification accomplishes by running each mesh size through a blue bowl by itself.

Many don't like this method because it takes more time. But I like it because I am a fanatic for getting all the gold that I worked hard for.

When you run each classification in a blue bowl you get a real time, visual look at what is being accomplished.

You can even assure yourself that the process works exceptionally well by trying a test run with unclassified material. You will quickly see the larger gold remain in place, while watching in dismay as anything smaller than the largest gold is swept out of the bowl as waste.

I shudder to remember when I first started dredging and knew nothing about either dredging or clean-up.
My Keene five inch triple sluice would produce a full five gallon bucket of cons to be panned. I actually panned the whole thing, it seemed to take forever since the place I was dredging held a lot of Hematite and Garnet sands. It was also difficult panning because of these heavies, I am sure now that I left a lot of fine gold behind in my panned waste.

After a time I learned to run my sluice cons through a small, clean-up sluice first, this helped a lot, but I still had to learn about screen classification, Now, when I do any clean-up I run each screen by itself, whether I am panning or using something like a blue bowl.

A lot has changed in my techniques over the years and each change has proven to increase fine gold recovery.



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Jim_Alaska
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geowizard
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Re: Gravity concentrator versus Wave table ( 23:58:40 ThuSep 28 2017 )

Jim,

Thanks for sharing that.

There really isn't any other way around it either. You can't assume it's all under a given mesh. Experience with the gold in a given location will show the range of sizes of fine gold. Then the process can be shortened to classify to the appropriate size(s).

- Geowizard

  

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