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Hi all.  I'm new here on the forums and to ICMJ in general.  I am not new to mining having had an exposure all my life, yet until the last few years, not too actively engaged beyond small recreational placer efforts.  I am the inventor of the Gold Well vortex drop riffle sluice, that some of you may have seen on the Bering Sea Gold show this year, and owner of HM Research out of Wickenburg, AZ.

 

Due to the fact that my sluice captures ultra fine gold, smaller than any other sluice so far as I am aware, it has come to my attention that many of my customers are unable to get all the values from their tailings.  (A picture through a microscope of fine gold captured in my sluice is at the end of this post.)  Devices such as a blue bowl, miners wheel, panning, even tabling, miss a significant amount of the gold (which can be recaptured by putting it back through the sluice).  In many cases, the amount of ultra-fine gold captured by the sluice exceeds the visible large gold.  This is of course no surprise, due to the fact that the majority of gold, at least where I am, is very fine gold.  I think that this holds true for most of the planet too.

 

This made me embark on a lot of research into different methods that might be used by my customers to recover their gold.  There are a lot of ways to skin the cat, unfortunately many of them are either too dangerous or too complex for the average small miner or novice.

 

The methods I have contemplated and tested are:

acids (aqua regia and other acid/halogen and oxidizer combinations)

mechanical means (blue bowl, cube, miners wheel, tables, etc.)

Have considered floatation but have not tested it yet

mercury and cyanide (I have tended to steer clear due to all the EPA and toxicity spectres it raises)

 

So here is the question I pose now.

What have I missed?  Is there a simple, effective, highly efficient method that won't get someone killed or cause major contamination, break the bank or be undesirable or unmanagable?

 

I have a mine here that we get good gold from, the particle size is near 1000 mesh which I use for testing the sluice recovery and performance, and to experiment with methods to recover the gold.  The ore runs 2 to 20 ounces a ton in the vein (the granite wall rock runs a few grams a ton.)  There are virtually no flat thin particles of gold, or even much visible gold in the ore.

 

Here is a picture of the gold from my mine near Wickenburg, AZ (taken through the eyepiece of my microscope with a cheap web cam.)  Sorry about the quality.  The line in the picture is a human hair measured at .003" (76.2microns).  Most of the particles appear like small popcorn balls about 1/3 to 1/6 the size of the width of the hair (12 to 25 microns).  This small particle size is not the result of crushing, as seen under a microscope, that is how they appear in the ore itself prior to crushing.

post-15870-0-95376900-1400635095_thumb.jpg

 

 

I do have a highly efficient mechanical method, but due to the fact that already people are emailing me telling me that they are
stealing my sluice design, I won't be releasing the device that I have invented for the mechanical removal and just use that for my own recovery purposes.  The sluice will have to be enough for everyone else.  So among standardly done methods, which direction should I head? 
Or do I just have to tell my customers that there is ultra-fine gold in their concentrates, and it's up to them to figure out how to get it out?

Producer2016 likes this

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Ok then let me ask this question:

Does anyone have a simple, inexpensive method to do floatation on small scale?  Like some kind of lab scale floatation cell that one could put together easy with easy to find things?  That might be an option that would be a fit.

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The problem with flotation is that it is not a simple "one size fits all" type of operation. Often successful flotation requires special tweaking for the individual ore.

Lab scale flotation tests can be done, but it works well for the treating of lab scale amounts of rock, like few pounds of ore, not for running a commercial scale operation where making a profit is the goal.

Normally, flotation gives a concentrate that needs to be smelted and there is just not easy access to smelters. The nearest smelter I know of which is accepting custom lots is in Mexico, and they want big lots of material, not a few pounds or even a few tons.

 

Is there a simple, effective, highly efficient method that won't get someone killed or cause major contamination, break the bank or be undesirable or unmanagable?

 

Nope. There is no cheap, effective, environmentally friendly way of recovering a high percentage of gold in the 1000 mesh size fraction. Experienced miners like you have been trying to do this for 150 years, and none have succeeded. Experienced Engineers, chemical experts and mining companies with multi-million dollar R&D budgets have tried too. No one has succeeded.

The closest thing out there for efficiently recovering real tiny gold particles is cyanide and hundreds of mining companies use it every day because it is so efficient and cheap. It is of course not for use by those who do not know all the hazards of using this potentially dangerous chemical.

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Hi Geowizard -

 

How are things going with your operation? (perhaps you could respond with a separate thread).

 

Yup, gold can be floated, and most prospectors who handle fine sized gold have seen flat flakes float even without help from pinesol and H2SO4 (sulfuric acid).

 

Its not done commercially because its hard to keep the flakes in suspension in a froth, but its an interesting concept.

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We, USAF active duty members in Alaska back in the late 1950's did a lot of stupid things in our quest for gold.When panning for gold, the remaining concentrate of heavy sands and fine gold presented a problem,separating the gold from the sand was a tedious undertaking with tweasers, kind of like picking fly chit out of pepper. An old established miner of the times told us of the why's and why not's(danger's) of using mercury to recover the gold. We midnight requisitioned some mercury switches from the electrical shop and drained them,smile.. the use of a two gallon mayo jar filled with  a small amount of mercury along with the concentrate when positioned on a motor driven paint shaker/mixer produced a gold amalgum glob. We had a 5 year engineering graduate  in our group who we all thought was the smartest guy in the world. He came up with a method of  making a mercury retort using a plumber's lead melting pot & blow torch and misc parts & pieces we had available at our radar site. I sure can't remember the details of how that rig all went together or worked, but it did work, allowing us to separate the gold and recovering most of the mercury as well.  I know we set it up outside and used a big fan to blow any escaping vapors away from us. It's a wonder we didn't kill ourselves from mercury poisoning. I'm sure we didn't expose ourselves or the surrounding atmosphere to enough vapor or skin touch to hurt anything but I'll bet we sure violated EPA guidelines to hell and back. I think back now on all the dumb tricks I did growing up and it's a wonder I survived.

 

dick

Geowizard likes this

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I know this is an older thread but here are a couple of possibilities for those that are still around and reading this.

 

You might consider this technique developed by Randy Clarkson.

http://yukon-news.com/business/new-gizmo-could-help-placer-miners-snag-lost-gold/

About as simple as it gets.

 Another system would be the Cleangold system.

http://www.cleangold.com/cleangold/home.html

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Fine gold concentrate can also be refined (upgraded) through several well known chemical processes.

 

For clarification;

 

"Refining" in this case is with reference to removing impurities at a micron and sub micron level. The process of recovery is a process that continually upgrades the purity through a process of concentration. A sluice box recovers gold as a concentrate which has greater gold content. Recovery is a process of eliminating non-gold products from gold. Gravity methods rely on separation based on mass. The particles must have nearly equal size and different mass to be separated.

 

There is a limit to the process of screening to smaller and smaller particle sizes during the recovery of gold. Chemical methods of recovery lead to an electrolytic cathode or precipitate. The precipitate can be melted.

 

Further concentration of gold involves improving purity and further refining.

 

The result is a 999 purity gold bar if done properly. :)

 

- Geowizard

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I read very well, thank you.

 

Gravity methods of recovery have a LIMIT.

 

To separate smaller gold, more screening is required to maintain compatible particle size.

 

Screening to smaller and smaller sizes becomes impractical at a certain point.

 

The process of catching gold includes clean-up where micron gold in concentrates is most often lost!

 

Flotation and digestion including amalgamation will increase recovery at the point where further screening is impossible.

 

Go to the top and read the first post. :)

 

- Geowizard

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The chemicals are used for recovery - not refining.

 

Mercury is used for recovery - not refining.

 

Flotation also uses chemicals for recovery - not refining.

 

Recovery of gold is a process of upgrading the gold to a pure gold end point. Since raw gold is recovered as an impure product, refining becomes part of the recovery process.

 

Splitting hairs doesn't contribute much to the discussion.

 

- Geowizard

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Flotation relies on the principle of "surface tension".

 

Miners wives observed gold floating in the suds when doing the laundry!

 

Cleaning the surface of the gold to be floated is done using a mild acid solution. Most acids do not react with gold but will remove other metals that might coat the surface and work to reduce surface tension. One metal that coats gold frequently is iron. H2SO4 is used by industry to remove rust. "Naval Jelly" is an example.

 

"Clean gold" will float with a little help!

 

 One off the shelf product is referred to as "Pinesol". Pinesol is inexpensive. It's available almost everywhere.

 

There is a difference between floating crushed ore with minimal exposure of gold and floating free gold with 100 percent exposure.

 

No, you can't float nuggets - but everyone has seen fine gold float in a pan. Add a drop of Pinesol and you will see gold float.

 

Detergent "suppresses" flotation. It is referred to as a suppressant. Gold panners usually keep a small squeeze bottle of liquid detergent handy to keep gold from floating while panning.

 

A flotation cell can be constructed.

 

A tub - almost any tub can be drilled and fitted with tygon tubing or other hose types to apply compressed air to the bottom of the tub. The objective is to agitate the gold in the tub when the tub is partially filled with water. A regulated supply of compressed air is provided and setup at an elevated level to eliminate reverse flow of water to the compressor.

 

Experimentation is required in any new endeavor that has variables involved. Unfortunately, there isn't a universal recipe!

 

Starting with a small, low cost flotation cell is easy.

 

- Geowizard

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Flotation is not a good method for fine gold recovery. Gold is dense and its ability to be floated is only fair. Flotation of gold has been done in laboratories, but it is not a commercially used method because of the difficulties involved, there are many methods of fine gold recovery which are better than flotation.

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