Drop Riffle Sluice / Angus MacKirk - capturing fine (flour) gold

X4FRNT

Jr. Member
Dec 5, 2019
56
72
Salisbury NC
Primary Interest:
Prospecting
I have two drop riffle sluices, a Angus MacKirk and a Robinson’s Brothers drop riffle sluice. They work great for capturing the larger gold flakes, but the flour and fine gold I find in my test pans are not being caught in either of my sluices.

I run the sluices with proper water flow and angled correctly and run classified material to 1/4”. After watching doc’s vid on Proportional Force multiple times I feel as though the fine gold doesn’t fall out into the drop riffles because the lack of disturbance/disruptions when using a drop riffle sluice. Angle and water flow play into this problem, lack of either means that it takes longer to clean the riffles and less material can be run through the sluice. Just wondering if anyone else is having similar issues, or if anyone has any advice on how to capture the fines from that upper water column.

I’ve been thinking of running the Robinson Sluice paired with the Angus behind it, and adding a damper before the material enters the Angus sluice. This would force the fine gold down into the lower water column and give it a chance to drop into the riffles. I’ll give it a try at least.

Thoughts?
 

RTR

Gold Member
Nov 21, 2017
8,180
32,468
Smith Mt. Lake Va.
Detector(s) used
Teknetics Liberator
Falcon MD-20
***********
Blue Bowl
Angus MacKirk sluice
Miller Table
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Love my MacKirk(for what it is) If you want to capture (flour) gold your better of getting a miller table.
 

KevinInColorado

Gold Member
Jan 9, 2012
7,037
11,369
Summit County, Colorado
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Grizzly Goldtrap Explorer & Motherlode, Gold Cube with trommel or Banker on top, Angus Mackirk Expedition, Gold-n-Sand Xtream Hand pump
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Prospecting
I’ve been running an AM Expedition for years. Several options:
1. Run the sluice with less water depth.
2. Classify to 8 mesh and run with less pitch& flow
3. Both 1&2
The sluice is capable if run for the conditions you face.
 

RTR

Gold Member
Nov 21, 2017
8,180
32,468
Smith Mt. Lake Va.
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Falcon MD-20
***********
Blue Bowl
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Miller Table
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One way to find out if the Angus is leaving fine gold behind. After you are all done running the material Place the material





into a pan with a few drops of liquid dish soap or Jet dry (used in dishwashers). This will break the surface tension of the water ,keeping fine (minus 100 mesh gold in the pan) from washing away.
 

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Duckshot

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Sep 8, 2014
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I have used a home built wooden drop riffle sluice to catch a bit of gold dust in WI. The thing is I have exactly no idea how much gold I might have lost, but I'm sure it isn't catching every grain. The only way to see exactly how much a sluice loses is to pan out everthing you originally ran through it. But, how do you know you are catching everthing in your panning?

Sluice it all again and pan it again? :dontknow:

It ain't a bad idea to test your tailings, but at a certain point you are better off just running fresh dirt.
 

Lefty2u

Jr. Member
Dec 21, 2013
28
28
Primary Interest:
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I have a large Mad Miner's sluice that I have removed the riffles out of. I have a 17 inch flare followed by 10 inches of inspection mat. This is followed by 17
inches of deep V mat. Next there is 6 inches of mother load mat. This is working very well on fine gold. I screen to 1/4 inch. I got help, information, from
John Doe. I am working a spot with only fine flood gold. Take a look at John Doe's posts.

Lefty2u
 

OP
OP
X4FRNT

X4FRNT

Jr. Member
Dec 5, 2019
56
72
Salisbury NC
Primary Interest:
Prospecting
I’m thinking of building a fluid bed sluice to run behind my drop riffle, that way I can still run 1/4” material at a good pace and have the fluid bed capture the fines that are still trapped in the water current. Picked up the materials to make it yesterday at Lowe’s and plan on building it this evening. Worth a try I suppose.
 

arizau

Bronze Member
May 2, 2014
2,479
3,854
AZ
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Beach High Banker, Sweep Jig, Whippet Dry Washer, Lobo ST, 1/2 width 2 tray Gold Cube, numerous pans, rocker box, and home made fluid bed and stream sluices.
Primary Interest:
Prospecting
I have two drop riffle sluices, a Angus MacKirk and a Robinson’s Brothers drop riffle sluice. They work great for capturing the larger gold flakes, but the flour and fine gold I find in my test pans are not being caught in either of my sluices.

I run the sluices with proper water flow and angled correctly and run classified material to 1/4”. After watching doc’s vid on Proportional Force multiple times I feel as though the fine gold doesn’t fall out into the drop riffles because the lack of disturbance/disruptions when using a drop riffle sluice. Angle and water flow play into this problem, lack of either means that it takes longer to clean the riffles and less material can be run through the sluice. Just wondering if anyone else is having similar issues, or if anyone has any advice on how to capture the fines from that upper water column.

I’ve been thinking of running the Robinson Sluice paired with the Angus behind it, and adding a damper before the material enters the Angus sluice. This would force the fine gold down into the lower water column and give it a chance to drop into the riffles. I’ll give it a try at least.

Thoughts?

To me it seems like not catching the fine gold is evidence that the riffles are packing up and not constantly "dancing" or exchanging. Not only can that cause you to lose fine gold but some of the larger particles too since they cannot penetrate the capture areas and are just swept across the top of them and out of the sluice. Swifter current and or steeper angle on the sluce may remedy this. Have you seen the videos here? https://www.google.com/search?q=ang...j46j69i60l2.5894j1j7&sourceid=chrome&ie=UTF-8. A couple of those show pretty extreme flow. I would say, run it flat in swift current and steepen it in slower flows.

Good luck.
 

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Gold4Mike

Full Member
May 10, 2017
230
718
Mount Vernon, Washington
Detector(s) used
Angus Mackirk Foreman
Grizzly Goldtrap Explorer
Gold Hog Piglet highbanker
Home made slate miller table
Primary Interest:
Prospecting
I've got an Angus Mackirk and it catches very fine gold. It can be a little difficult to run one sluice behind another, but you can sure test the losses of either one of your sluices by running the other right off the first. It would be an interesting test of either one.
 

Goldwasher

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May 26, 2009
6,077
13,222
Sailor Flat, Ca.
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if the first sluice doesn't catch fine gold.. it isn't gonna get caught in second sluice.

No matter what type the second is.

The best bet for getting more gold in your sluice. Is to run dirt that has more gold in it.
 

KevinInColorado

Gold Member
Jan 9, 2012
7,037
11,369
Summit County, Colorado
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Grizzly Goldtrap Explorer & Motherlode, Gold Cube with trommel or Banker on top, Angus Mackirk Expedition, Gold-n-Sand Xtream Hand pump
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if the first sluice doesn't catch fine gold.. it isn't gonna get caught in second sluice.

No matter what type the second is.

The best bet for getting more gold in your sluice. Is to run dirt that has more gold in it.

Often true.
Unless the first sluice sucks or is set up poorly. I once put a fluid bed below a friend’s WolfTrap Hungarian riffle sluice and it was amazing how much gold I caught. The friend was just horrified lol!
 

Goldwasher

Gold Member
May 26, 2009
6,077
13,222
Sailor Flat, Ca.
🥇 Banner finds
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SDC2300, Gold Bug 2 Burlap, fish oil, .35 gallons of water per minute.
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Often true.
Unless the first sluice sucks or is set up poorly. I once put a fluid bed below a friend’s WolfTrap Hungarian riffle sluice and it was amazing how much gold I caught. The friend was just horrified lol!

True if the first sluice isn't good hopefully the second will catch some. I guess what i'm getting at is if the first one is working right the second isn't gonna kick in on what isn't held by the first.

I was mainly referring to the fine gold that is at the lower end of the catch rate anyways.. That if water speed has kept it moving... is very unlikely to drop out of suspension.
 

mytimetoshine

Bronze Member
Jun 23, 2013
1,574
3,370
El Dorado County
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GRIZZLY GOLD TRAP - ANGUS MACKIRK EXPLORER- BLUE BOWL - GOLD CUBE, MINELAB PRO 25 PINPOINTER-
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I have no problem catching dust with my Angus Mackirk drop riffle.... In fact it has the best recovery imo, but you have to have proper exchange going. It's not about water speed and angles. If the material exchanges properly then it will catch. if it's getting packed up then it will blow gold all over the place
 

arizau

Bronze Member
May 2, 2014
2,479
3,854
AZ
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Beach High Banker, Sweep Jig, Whippet Dry Washer, Lobo ST, 1/2 width 2 tray Gold Cube, numerous pans, rocker box, and home made fluid bed and stream sluices.
Primary Interest:
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Check this drop riffle design out. Note that he has it set up in a switchback design as a highbanker.

 

Duckshot

Silver Member
Sep 8, 2014
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Check this drop riffle design out. Note that he has it set up in a switchback design as a highbanker.



That first drop down ain't catching nothing. The material does not appear to have been classified, he's sending it down in clumps. I didn't even watch the whole thing.

ETA- it's not a bad design for a sluice, but it needs adjustment IMO.
 

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Goodyguy

Gold Member
Mar 10, 2007
6,489
6,895
Arizona
Detector(s) used
Whites TM 808, Whites GMT, Tesoro Lobo Super Traq, Fisher Gold Bug 2, Suction Dredges, Trommels, Gold Vacs, High Bankers, Fluid bed Gold Traps, Rock Crushers, Sluices, Dry Washers, Miller Tables, Rp4
Primary Interest:
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That first drop down ain't catching nothing. The material does not appear to have been classified, he's sending it down in clumps. I didn't even watch the whole thing.

ETA- it's not a bad design for a sluice, but it needs adjustment IMO.

That first tray seems to be doing a good job of stratifying material for the next 3 runs, similar to what the top tray on a gold cube does.
Would be interesting to see just how much gold is being captured in the first run if any.

GG~
 

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Duckshot

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I see what you are saying. But there has to be better ways to break stuff up than flat boarding it over deep drop riffles. In my favorite home built drop riffle the first 8" or so are 1/4", 1/8" deep dados spaced 1/4" apart. Imo it pays to have a drop riffle with a couple different shaped riffles. The plastic drop riffles that are just three feet of the same sized riffles never made much sense to me. If my sluice can't catch gold going past in a foot worth of riffles, I want to try different riffles.
 

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