Lets Talk About Fine Gold --'

[PickaxeCA]

@geowizard - I appreciate hearing your stories from experience. As a recreational miner I wish there was more info like this out there--- real battles with fine / flour gold, at an industrial scale.

Just wanted to look at the following statement you made:

"Given a 12 inch sluice with a water pump running at 2 gallons per minute..."

I don't recall seeing anyone recommend 2 GPM for a 12 inch wide sluice. That would be 160 GPH which would only work in a 1 inch wide sluice, which certainly isn't practical.

Rather, here are the numbers I could find from their respective sources (per foot or 12 inches of sluice width)

Poling and Hamilton: 160-200GPM = 9,600-12,000 GPH
PopAndSon - HIGH: 80 GPM = 4,800 GPH
PopAndSon - LOW: 20 GPM = 1,800 GPH
Gold Cube - HIGH: 30 GPM = 1,800 GPH (with hose loss on 2,000 GPH bilge pump)
Gold Cube - LOW : 15 GPM = 900 GPH (with hose loss on 1,100 GPH bilge pump)


I personally run the following in my 6 inch sluice:

A 1" Honda gas pump, 2/3 throttle = ~25 GPM = 1,500 GPH (would be equivalent to 3,000 GPH in 12 inch sluice)
A 2,000 GPH bilge pump = 30 GPM = ~1,800 GPH with hose loss (equivalent to 3,600 GPH in 12 inch sluice)

It appears as though my operating parameters are near the low end of PopAndSon guidelines above, though if I was in an area with little to no -150 mesh gold I would crank up the water to a way higher GPM / GPH for more throughput with pretty much the same coarse gold capture.

[PickaxeCA]

Yes ChickenMiner, there is more information and tools available then ever on the topic of fine gold capture. This is great for placer miners today of all scales.

I think people get caught up in matting opinion wars far too often rather than focusing on operating parameters that could work with nearly any capture media as long as it's low profile.

The matting is merely one variable in a system.

[Geowizard]

Pickaxe,

You come across as being more intellectual than the average placer GOLD miner.

Welcome!

All too often in placer operations, the weakness is in being haphazard. Success is found as in other endeavors, in what would on the surface appear to be a simple process and the process becomes more of a "science project". Reading about the methods used by recognized experts like Pop and Sons and Jason at MBMM and watching it on venues like YouTube goes a long way in setting the stage for base line studies. Setting up stable, repeatable and measurable conditions really requires a stable working environment like a laboratory in the garage. You point out the issues of variables and variability in the process and that point is critical in this work.

In many cases, I have seen conclusions made on methods and systems being "good" or "bad" based on poor or inadequate measuring methods or techniques that bias the results. Without measuring the amount of GOLD going in to a recovery system, the recovered GOLD may be NO GOLD and the system is therefor a bad system and the opposite conclusions are made on the same system in a different environment.

One possible matter of concern to me is doing the same thing as others and expecting a different result. We can naturally do the same things as others and expect to get the same result. Fine GOLD recovery gets into a realm of slow motion physics that the placer mining world in general does not appreciate. The flow rates have to be turned down. When flow rates are turned down and feed rates are turned down, changes in a test setup have to be made on a smaller scale with greater attention to precision in measurement. Screening becomes a critical component as well as recognizing particle shapes. The composition of the slurry affects the ability to segregate GOLD from a surrounding mix of similar masses of black sand particles and ultimately gets down to fine details of the dynamics of what the composition of the black sand is. Cassiterite (Tin Oxide) is a type of black sand found frequently in Alaska placer mining operations. It represents a unique challenge.

You mentioned the subject of fine GOLD recovery from hard rock. Crushed and milled rock with angular faces and the recovery of GOLD when the GOLD is angular and of unlimited shapes as you eluded becomes a whole new ball game. I have rarely seen much discussion here about that. I'm looking forward to more discussion on the subject!

- Geowizard

[Geowizard]

An Oxymoron;

Fine Gold recovery is an oxymoron. The terms are incompatible. In the real world where GOLD recovery by means of GRAVITY separation takes place, the force of gravity becomes insignificant as particle sizes become smaller.

That's just the simple reality of physics.

In our small minded world of political correctness, terminology related to recovery methods that are well known in the art and science of fine GOLD recovery are no longer acceptable. We cannot use the "M" word. We cannot even use the letter "M" as "code" in discussion because "We" know what the letter "M" stands for!

Back to the subject of fine GOLD recovery using GRAVITY methods. As GOLD particles become smaller, more screening is needed to reduce the size of competing particles - "heavies" that want to stay in the pan or sluice while the "lighter" particles of "fine" GOLD return back to where they came from! Pure and simple, them's the laws of physics!

There's only one, much more complicated solution...

The solution is to screen down the particles using progressively smaller screens. That process is tedious and time consuming. When I say tedious and time consuming - I am speaking of the type of slow motion and patience that result in abnormal psychological behavior. I'm serious. I have worked with patients in psych wards suffering from "fine GOLD recovery syndrome". I don't recommend this type of work for the sissy types of Gen-Y and Z.

https://en.wikipedia.org/wiki/Millennia ... meline.svg

If you care about your personal mental health, don't do it. The practice of shaking a screen repeatedly and going from one screen size to the next using buckets of water while keeping track of which size went in which bucket scooping the sand and shaking over and over will leave you bent over, "stuped" and eventually "stupid". Trust me, I know!

- Geowizard

[Geowizard]

Frog's Fur;

There are well known methods used to recover fine GOLD that have been around for quite awhile. One rarely seen method is the "cleangold" method.

http://www.cleangold.com

The challenge for gold miners and prospectors comes not from fine gold but the new world order that is driven by a propaganda machine. The propaganda machine distorts the reality of safe, efficient fine gold recovery using mmmm and known over the counter chemicals that digest gold into solution and from which the gold is recovered (precipitated) using zinc.

Gold is found in nature on all scales from fine gold visible on a microscope down to micron gold, sub-micron gold and nano-gold. Eventually, fine gold recovery using gravity gets down to a level that mankind has to resort to matting that is fine as frog's fur!

- Geowizard

[Geowizard]

Laminar flow;

The common method of recovering fine gold using a sluice box includes riffles and a variety of means and methods of lifting and rolling the flow of water in an attempt to get fine GOLD to settle in place. A more subtle approach involves taking a view of the concepts used in recovery methods like the Miller table.

Nome Alaska is in many ways the poster child for fine GOLD recovery. Looking at the sluices used in the early days, the most casual observer will note that the boxes they used were "Long Toms". Some of those boxes were 100 feet or more long! The drop was minimal. The matting was in the form of fabric similar to cheese cloth. A fabric called Corduroy was also used. The water flow was laminar. The laminar flow allowed fine GOLD to settle into the fabric matting.

- Geowizard

[PickaxeCA]

@Geowizard - to your extra long Nome wash tables I would add the following:

On the Snake River in Idaho (known for very fine gold), they used very wide 'wash tables' covered with burlap cloth. Same thing - low angle, low turbulence, low profile matting.

I have read that old stamp mills used a beach-box-like wide and slow sluice covered with corduroy, burlap or similar to catch very fine hard rock gold.

They use something similar on the Danube River in Europe. Bascially, beach boxes using wool blankets or similar, with no expanded metal. Almost like a giant, textured miller table.

My favourite analogy for catching very fine gold is to start with a miller table, and work your way up from there in terms of texture, flow, angle, feed rate, and feed classification.

If a miller table can do it with no riffles, surely one can design a sluice box to catch -200 mesh to -325 mesh and beyond flour gold (assuming they have the patience for low enough rates of flow, feed, angle and classification).

As you mention, the shape matters A LOT. A 200 mesh boulder may be much easier to catch than a 40 mesh tinfoil flake that sails down a sluice uninterrupted.

Therefore, I wonder if hard rock gold is easier to catch at smaller sizes than placer gold in some circumstances.

Dan / Pickaxe

[Geowizard]

Theory of Relativity in placer GOLD mining;

When I looked at all of the GOLD recovered over the past decade at my wild Alaskan placer diggin's, it looked like 20 mesh flying saucers! I didn't see any space people!

Basic aerodynamics applies to hydrodynamics in the same manner when LIFT and flying and gliding are considered! With appreciation of that fact, if and when the flying saucers of GOLD are moving at the "same speed" as the fluid surrounding them, there is NO relative motion and there is NO lift. The flying saucers in my sluice box produced NO lift and landed safely in my sluice box!

Geowizards "Theory of Randomnymity":

With random shapes, "random shape is too random". The rolling, tumbling forces all add up and subtract in opposite directions and equal net ZERO inertial Force. The ONLY salient forces at play are Mass of GOLD and the Mass of water/slurry. Newtons second law of motion applies. Force = Mass x Acceleration.

https://www.thoughtco.com/what-are-newt ... ion-608324

Fun stuff!

- Geowizard

[Geowizard]

100 mesh GOLD;

The micron stage has a 1 mm, electron sputtered, silver scale (looks like a ruler) divided into 100 divisions.

On a scale of .01 mm = 10 microns per division.

For reference: 100 mesh = 149 microns (15 divisions).

https://www.industrialspec.com/resource ... ron-sizes/


At Ophir Creek Mine, I bagged up twenty, one kilogram bags of my saved screened 20 mesh minus reject cons for further testing during the off-season. The bags contained 70 mesh minus GOLD in black sand. A 20 mesh screen will only recover 70 mesh GOLD. I had saved the "minus 70".

We want to recover the 100 mesh!

Here's how:

The way gravity recovery works is the "lighter" particles go away and the "heavier" particles stay behind. It's actually a matter of "mass". Mass includes volume of the particle.

Pure Gold has a mass of 19.3 grams per cubic centimeter. Placer Gold is around 15-19 grams per cubic centimeter. Black sand hematite or magnetite on average is 5 grams per cubic centimeter.

https://www.scribd.com/document/210274359/Black-Sand

No problem if their size is the same!

Black sand heavies have equal or greater mass than GOLD if they are FOUR times larger. Sand and limestone having TEN times the size also have equal or greater mass than GOLD.

To level the playing field, the particles have to be classified by screening! The Mass of GOLD and other particles increase 4X with a 2X increase in diameter.

If you screen to 20 mesh (841 microns) you cannot recover GOLD smaller than 70 mesh (210 microns).

To catch 100 mesh (149 microns) GOLD, you need to screen to 80 mesh (595 microns).

Anyone that has done it will agree, screening to 80 mesh using 5 gallon bucket screens is a slow and very tedious process. Screening is done in steps using progressively larger mesh screens starting with 4 mesh, then 8 mesh, then 16 or 20 mesh. To catch 100 mesh GOLD requires TWO more screens; 40 mesh and 80 mesh.

Screening to 80 mesh will catch the 100 mesh GOLD.

The "minus 100" GOLD fraction cannot compete and goes overboard. That becomes the next project!

- Geowizard

[PickaxeCA]

@geowizard - processing buckets of black sand for -100 mesh gold is a different process indeed, with its own set of rules!

If it was me, I would buy some 100 mesh screen on a roll, cut a 3 foot long piece of it, and use it in a tub, grabbing both ends, lifting up and down, and turning the material over on itself. Seems like that could be way faster than a bucket classifier.

Or, make a 100 mesh screen 'shaker deck' and use with a vibration motor to dewater and clear material.

Or, just use a vibration motor with the 80 mesh bucket classifer ; )