Lets Talk About Fine Gold --'

[Joe S (AK)]

LONG ago, in the late 1880s talk about "fine gold" was usually preceded with a disgusted growl by the old timers. NOBODY wanted to bother with that stuff.
Virgin ground yielded lots of large to moderate sizes and it was just not profitable to take the time to go for the small stuff (except for those wise Chinese miners, of course.)
Even until the mid 1960's that was the mantra.
Small gold was thrown back into the stream as worthless (at $17 to $35 an ounce) and mining was thought to be profitable on just the larger 'stuff'.
Early on in "My Beginning Time" I became fascinated with this forgotten gold. Over the years the small stuff became more and more compelling. Why not learn how to to recover it since it was just sitting there anyway?
Over time I learned that "old timers" were actually wrong by promoting shallow, smooth, slow water with the assumption that small Gold just had to quietly settle or it would just wash away.
As it turned out, small Gold is actually better trapped by controlling the water flow rate to wash away lighter heavies, while not washing away the powder Gold. By providing various shallow catchments to store the now settled Gold that was now trapped.
Small placer Gold does come in an infinite variety of shapes and because of that a variety of catchment shapes were also needed.
While seemingly complicated in theory, the good news is that once set up the results are amazingly simple. The hardest part is to just break old habits.

[Joe S (AK)]

Well, it seems nobody wants to address the subject of fine Gold.
Fair enough - just what do folks here want to talk about?
This forum was started, long ago, to share Gold mining knowlege and I, silly old me, thought that folks would enjoy talking about the subject of small Gold. We've all found it so why not share our knowledge on the subject? Am I wrong and is it of no interest here?
I believe that we all need to share knowledge about the winning of Gold from our efforts in our various operations - am I wrong?
It seems to be time to stand up and share our combined knowledge --- or get off the pot.
Am I wrong? If so, then just say so and I'll quietly move over to let a more knowlegable miner set me straight.
C'mon and put your head up and 'er rip!
Joe

[easy goer]

Joe

Crazy busy! I am familiar with fine gold. This summer I found ONE piece of gold that was +16 in size. 90% of what we found was -30 or smaller. I will write more when able.

Easygoer

[chickenminer]

We have to mention the fine studies done by Poling & Hamilton and the Clarkson(s). Mainly aimed at larger operations the information bonanza in those studies can be used by anyone after placer gold with a gravity recovery system.
Clarkson studies;
https://www.scribd.com/doc/61880538/The ... d-Recovery
https://emrlibrary.gov.yk.ca/ebooks/kpm ... rading.pdf

Hamilton;
https://www.westcoastplacer.com/Files/1 ... ce-box.pdf

[Joe S (AK)]

Dick,
As I understood the Poling and Hamilton studies (resulting in the Miner's Moss with expanded over) was envisioned and funded by (I think) the Yukon Provincial Government as an attempt to increase the recovery % of Gold from the provinces' medium and larger operations.
While it has been a while since I read the reports, I vividly remember that the recovery factors in the various provincial operations was as bad as 50%.
Most of us know that up until the moss 'n expanded came along a very high % of small Gold was just "catch and release". All sorts of riffle styles from just big rocks, wooden riffles over any sort of carpet materials to rail road rails were haphazardly (sp?) Used to try to create catchments for traveling Gold. The moss 'n expanded dramatically increased the common sub-standard recovery systems - especially in small Gold sizes.
All that happened in the '70s and as the normal ways of 'things' go that was held to be the absolute best type of recovery of all time (by the set-in-their-ways miners back then).
Over the years there has been a LOT of further research done. Old thinking, based on old "established" ideas has had to step aside over the years for now proven advancements.
We've all heard about some of them --- Le Trap, Gold Cube, Vortex Matting, Gold Hog, Saw Tooth Mats and many, many more. Some are sometimes better suited to certain Gold characteristics in certain areas however in a general way the newer products do out perform the old standard Hungarian riffles (or the up angled angle iron ones) in quantity and sizes recovered - which was the standard for many decades.
I am reminded of a miner in Australia who, independently of emerging products, was working on a very unique, personally conceived, riffle design for his own operation. He spent 6 or 8 years designing a riffle shape (in cross section and riffle spacing) which he finally found would efficiently recover the 2 mm target particle size for Gold and Platinum in his operation. Phil found the ultimate solution for the 2 mm target sizes of his pay - just about the time that a sunrise motorist hit him and ended his mining days. Phil, with all the healed bones and surgery over is still forging new ideas and I almost got to meet him in '19.
Maybe next time, Phil. - Joe -

[Geowizard]

The recommended feed rate:

https://www.westcoastplacer.com/Files/Clarkson1990.pdf

- Geowizard

[PickaxeCA]

Hello all,

Here are my thoughts plus a framework for discussing fine gold recovery.

It's worth mentioning that hard rock gold can be chunkier than placer pieces that have been hammered flat. Therefore, it may be easier to catch smaller hard rock gold with light to moderate feed, flow, angle, and very small classification (e.g. 20 mesh). Still, let's include both placer and hard rock gold capture when discussing fine gold.

----

SCOPE / ASSUMPTIONS
Gravity separation only (no mercury or other chemical processing).
Sluices only - no jigs, centrifuges, etc
Non-river sluices only (enables complete control of variables)
Low-profile matting only (no angle iron riffles)
Equipment weight not included as a factor

INDEPENDENT VARIABLES
Gold size: 20 mesh and smaller (anything bigger than 20 mesh is easy to catch if it's not tinfoil thin)
Classification size: variable
Flow: variable
Feed: variable
Suspensed solids: variable
Capture media: variable
Gold size: variable

DEPENDENT VARIABLE
Gold capture rates: at various mesh sizes down to 400 mesh (the practical limits of gravity separation)

------------

I'll rely on the data from the PopAndSon sluice study, as they summarized findings from other researchers.

PopAndSon: search online for: "PopAndSon sluice"

-------

Poling and Hamilton (link to source is below)--- industrial sluicing with excavators
Water flow: (per foot of width) 160 GPM (9,600 GPH)
LB/minute feed (per foot of width): 300-400 lbs (equivalent of 5+ 60lb buckets a minute in a 12 inch sluice!!)
Slope: 1+5/8"
Capture media: expanded over nomad (3M brand miner's moss, for those who don't know)
Recovery:
99% of 65-100 mesh - this is very high for the flow and feed rates above!
83%, 100-150 mesh - still quite good considering the high feed / flow rate

"Good recovery of gold should be expected at a feed rate of 300-400 LB / minute of solids per foot of sluice box width accompanied by approximately 200 GPM (US) [ ed: 160 GPM imperial ] and a box slope of 1+58" to 2 inches per foot."
(P. 1 in report, P 6/73 in the PDF)

"The recovery of fine gold may be improved by having short sections of smooth, unriflled sluice box interspersed with sections of expanded metal riffles, for example--- 4 feet of expanded metal riffles followed by 2 feet of smooth box [ed: bare moss with no expanded ]."
(P. 2 in report, P 7/73 in the PDF)

"Further research would be beneficial, such as:
A) Using different riffle types
B) Processing different gravel types
C) Using very fine gold"
(P. 2 in report, P 7/73 in the PDF)

Source: https://emrlibrary.gov.yk.ca/ygs/mining ... placer.pdf

------------

PopAndSon Sluice Project

Following the findings of Clarkson, Poling, Hamilton and others, Steve and Jason Graber in Washington State (Mount Baker Mining and Metals) did some independent research and shared their design schematics and results for anyone to use.

Their PopAndSon sluice has one of the best documented recovery rates for very fine gold down to 325 mesh and beyond. There are reports of their sluice capturing 400 mesh hard rock gold.

There is a YouTube video with Jason from MBMM showing 100 - 325 mesh gold and -325 mesh in two separate pans. There was a considerable amount of gold in the -325 mesh pan.

https://youtu.be/k1nJfGJrJf0?si=NK_uE8g1-VW2ZXXD&t=524

Note: the PopAndSon sluice caught 90% of the gold down to 325 mesh, and the shaker table caught the remaining 10% of catchable gold in their sample.

This suggests that their base sluice design of 3/16 expanded metal over backed or unbacked miner's moss (3M Nomad) works extremely well for gold down to 325 mesh and below---even at higher feed rates than you might expect.

A now defunct operation in Alaska called Goldman Engineering processed the gold room tailings of placer miners in Alaska who couldn't get more gold out of their concentrates. Their approach was to run black sand through a ball mill, and then over a long PopAndSon sluice with 2 different sizes of expanded metal: 1/2 inch (top of sluice) and 3/16 (bottom of sluice). This tells you the PopAndSon was catching what the professional placer miners could not in their gold cleanup rooms.

Goldman Engineering gold recovery - PopAndSon in action, scavenging gold from previously-ran concentrates:
https://youtu.be/KdikUKNLCHY?si=QbqhzcbJe5zt2-X8&t=124

----
PopAndSon Sluice: Specifications

Reference sluice: 12 inches wide, by 48 inches long (4 feet)

Capture media:
3 different sizes of expanded metal (3/4”, 1/2” for chunky gold, and 3/16” for flour gold)
3M Nomad miner's moss (unbacked with V matting, or backed)
Dampener flap (clear Visqueen plastic, extending for much of the sluice length)
Classification Size: 1/2" to 3/4" maximum (1/8" is ideal, 1/4" works well)
Slope: 1.5 inches / foot
Flow: 20 GPM (1,800 GPH), in a 12 inch wide sluice
(2,000 GPH bilge pump with 5-6 feet of hose would work well here, or a 1" gas pump)
Capture rate:
+95%, 100-200 mesh, “corn flake”gold
+85%, 200-325 unknown gold shapes

Examples of PopAndSon sluice in action:

Gas-Powered Mobile Hammer Mill for High Recovery Gold Mining in Remote Areas - MBMM
https://youtu.be/V5-nInj_kYQ?si=x5V4gZnp4xbwVzU2&t=258
90% gold capture from 200-325 mesh in this particular test, at moderate rates of flow and feed (confirmed in the video below)

Testing Sluice Box Tailings For Fine Hard Rock Gold Recovery vs MBMM Shaker Table
https://youtu.be/k1nJfGJrJf0?si=NK_uE8g1-VW2ZXXD&t=524

--------------

I am not biased toward the PopAndSon sluice, but they have some of the best data on fine gold recovery for small-scale miners. Other researchers such as Clarkson, Poling and Hamilton certainly showed what's possible at an industrial scale with very high rates of flow and feed, but PopAndSon translate this down into what's practical for small operations, even hobbyists.

My objective with listing the info above is not to steer anyone toward 3/16" expanded over blue Nomad miner's moss from the PopAndSon design. It's more to establish a general set of operating parameters to give any capture system the best chance of success. It also allows system performance to be compared head-to-head, in an apples to apples comparison.

By standardizing fine gold capture discussion to a 12 inch sluice (which can easily be operated with any 2,00 GPH bilge pump or 1" gas pump if targeting fine and flour gold), we can make establish a baseline recipe that people can follow using any sytem with low-profile matting.

Want a different sluice size e.g. 6 inch? Simply divide the parameters for a 12 inch sluice by 2. An 8 inch sluice divide by 1.5. For a 10 inch sluice divide by 1.2.

Personally, I am astonished by how high some of the water flow and feet rates are. I have never slammed that much material and water into a sluice before, but I also trust their findings, so maybe I need to step up my flow and feed!

What are your thoughts on the above?

Does anything surprise you, or stand out?

How would you apply it to your type of material or sluice setup?

-----
The following brands, materials or setups are known to be good to excellent for fine gold recovery:

SLUICE CONCENTRATOR
Multiple sizes of expanded metal (3/16" or 1/2") over #3M Nomad miner's moss (PopAndSon)
Multiple sizes of expanded metal (1", 3/4" 1/2") over alternating Nomad miner's moss and astroturf (Freddy and Juan's Mine Rescue show---their most used setup for helping struggling miners recover more fine gold)
Gold Cube (+/0
Gold Hog
Dream Mat
Ribbed carpet (on its own, or with expanded over top)
Rough top conveyor belt (same matting as in the Gold Cube)
Goldwell Sluice / Devin Gold Sluice
Drop Riffles - Le Trap, Geosluice, etc
Angus Mckirk - at low feed rates, with tight classification
Felt - John in Edmonton ran his season's concentrates 7 times, then ran again over only felt in the sluice, and recovered an additional 1 gram of flour gold. - Source: https://www.detectorprospector.com/topi ... you-think/
Beach Box (Nome AK style)
V matting (shallow) aka ribbed runner matting - example is George Massie in his flour gold capture video using a 2ft W x 6 ftL Beach Box w only V matting, with a small section of 3M Nomad at the bottom (going into diverging poop tubes):
FINE GOLD RECOVERY ON THE BEACH OF NOME, ALASKA WITH GEORGE MASSIE - GPAA ARCHIVES
https://youtu.be/8jiJOT53OLg?si=1xy5hHtuPvWOPVFJ&t=38

Polar fleece - large wash tables in new Zealand pumping 8 yards of beach sand per hour for 4-5oz/week of gold - "https://community.paydirt.co.nz/t/histo ... ube/3683/6

"We would pump about 8 cubic yards of sand an hour over the tables. Usually running around six hours a day. Weekly gold production was between 4 to 5 ounces."
"The next mission was to find some sort of matting that wouild hold the fine gold. I wasn’t going to go the mercury/copper plate way. After testing many different materials I found the best for the ultra fine beach gold [ed: 4-5 oz/day out of 8 yards of sand/hour] , was believe it or not was inside out sweat shirt fabric, polar fleece was its name. And boy did it capture and hold the gold. So that became my mat of choice." - KiwiGold

---------
CONCENTRATE CLEANUP (AKA CLEANUP SLUICE) - OR HARD ROCK GOLD CONCENTRATOR
CleanGold - sort of like a magnetic V mat, corduroy pattern - gold gets caught in black sand 'riffles'
PopAndSon sluice (3/16" expanded over Nomad, 6" wide x 4ft or longer sluice
Gold Cube
Rough top conveyor belt (same textured rubber matting as the Gold Cube)
V matting only
Drop riffle (Le Trap, Devin Gold, Geosluice Bucket Sluice, etc)
Dream Mat - Micro Mat
Felt sluice
Keene A52, A51 sluice - ONLY if adding concrete vibrator (can catch well below 200 mesh if using a vibration bed like in this video):
Capture Fine Gold With A Simple River Sluice Modification - Aussie Bloke Prospector
https://youtu.be/kMLD-SwRLpE?si=VKoqaKIiCps9e-7D&t=696
---------
FINAL CONCENTRATE CLEANUP
Miller table
Blue bowl
Felt sluice or similar

[Geowizard]

The voice of experience:

I went out on a limb during the 2007-2008 financial crisis to prove a placer miner could mine enough GOLD in Alaska to feed his or her family. I designed and fabricated three wash plants and shipped 'em up to Alaska.

The Maxi Bankers;

The Maxi Bankers were constructed of an aluminum .125" diamond plate sluice box in two 8 foot sections in series, three feet wide with a screen, hopper and spray bars. They were designed to be transportable by air in a Cessna 207 anywhere in the bush where a 207 could get in. The only tools required were two 9/16" combination wrenches to assemble the wash plants. The pump was a Keene 23 HP Vanguard Engine & Pump w/Electric Start. Six inch intake and 4 inch outlet. The pump could push 600 gallons per minute operating at 70 percent power. The sluice boxes had 3/8 expanded metal over Astro-turf. Occasionally, I went to miners moss, Cocoa mat, ribbed mat and tried all of the variations of Gold Hog extruded rubber mats over a 12 year period.

I mined $20 per yard tailings at the rate of 50 yards per hour for 10 hours per day. The GOLD was all 20 mesh minus. I used two - one yard Bobcat Skid steer loaders to feed the wash plants. I had 7 million cubic yards of tailings along the creek - all at eye-ball level.

I learned about "fine GOLD". The stuff you can't recover using conventional means. Yep, I read the Randy Clarkson report and listened to all of the "experts" here on the Alaska Gold Prospecting Forum.

Everything was tested, retested and calibrated.

What could possibly go wrong?

Stick around and find out!

- Geowizard

[Geowizard]

Doing the fine GOLD math;

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

Randy Clarkson recommended a 30 percent slurry. That's 30 percent solids in the sluice. At 2 gallons per minute = 120 gallons per hour, the sluice should run 40 gallons of solids per hour.

One cubic yard represents 200 US gallons. A little math shows we are running about 1/5 of a cubic yard per hour and without interruption, about one cubic yard per five hours. That cranks out to TWO cubic yards per ten hour day.

Assuming a miner is "in certified $20 per cubic yard GOLD", that washes out to a modest $40.00 for a ten hour day.

Gasoline runs around $10 USD per US gallon out in the bush. At two gallons per day, the fuel cost is $20.00. Net pay after gas is $20.00.

Cleanup takes several hours.

FINE GOLD is a slow cleanup process that requires patience in screening down to the size of the fine gold. If it really is 100 mesh GOLD, screening the cons down to 100 mesh is the rule of the day. The particle sizes have to be compatible for GOLD to stay in the pan.

Who wants in?

Don't go away! There's more!

- Geowizard

[chickenminer]

Pickaxe,
Welcome aboard! Thanks for posting. Fortunately for miners today there is a wealth of information on fine gold recovery at our fingertips. All we have to do is figure out the best combination for our particular operation and gold type.