Dredges and fine Gold?

[Geo-George]

I've always run a sluice and pan. Once in a while I come across someone dredging.
Never bothered 'em, they were busy.
While watching the water flow over the short sluice box, I was wondering,
how one could possibly trap any fine Gold. Seems like it's a deep fast flow,
and would wash out a lot of finer Gold. I don't run my sluice (18' long tom) near that fast.
What am I missin'?

The ban came through about 2wks before I could file, but I'm ready with a "Simple Simon"
as soon as we can go dredging. (gotta keep the faith )

[CalGoldDredger]

Use of Under/Over sluice box where material is classified and drops to a slower under current box.
The riffle design has a big effect and are different than the hand sluice.
Last but not least use of miners moss or comparable, this stuff can hold a lot of fine material.
Where I operate I don't see a whole lot of fines nor do I set-up my recovery for them but most of my gold is in the first foot of the top of the sluice including any fines and anything that may be blown out of there is trapped in the under box roughly 10% of the recovered gold.

Yep, hope we will be dredging real soon.

[Hoser John]

Header and jet style predicates recovery to even the over under style boxes. You didn't post either so not much info to go on. Flares spread'r out,deaireates, and drops that righteous gold right quick like into the first set a riffles or the under box. Never use a backed carpet anything in a dredge as instant impaction and adios to that righteous oro puro that your desperately trying to find-tons a au 2 u 2 -John

[misterbigtoe]

When dredging, as soon as gold bearing gravels are loosened, mixed with and suspended in water and begin the trip up the dredge hose, the gold begins to settle out of suspension. Of course, the finest of the gold is the least likely to fully settle before hitting the sluice. Therefore, upon exiting the suction hose, the suspended gravels, sediment and metals travel through the flair where the water spreads out and slows down prior to crossing the recovery media. This spreading and slowing of the water allows the fine gold to settle and even a relatively short sluice does a good job of trapping the gold. Helps to think of the entire suction side of the dredge as part of the the recovery system with the suction hose and flare functioning as the very upper end of a very long slick plate.MBT Eric

[Geo-George]

I get it!
Thanks!

I would think that so many gpm, requires certain dimentions for the sluice?
Right?

[misterbigtoe]

There are nearly infininte variables, but a starting point in a riffled sluice is a couple of hundred gpm per foot width of sluice at a drop of around an inch per foot. This is assuming a relatively steady feed of completely washed and properly classified material say.........-3/4 inch. That being said I have worked quite successfully well outside of those parameters in situations where our entire output consisted of fines and our losses so insignificant as to be nearly incalculable. Undoubtedly the single most important factors in recovery is proper washing and feed rate..............avoiding surges and riffle fouling. I have had to sluice at much higher than optimal flow rates for the width of sluice I have had available and adjusted angle and length of the sluice to accomodate this. Conversely, I have had to sluice with far too wide of a box which had be set at nearly 2" per foot over 38 feet and still had to have a boomer standing in my sluice with a spray nozzle to keep material moving! Ultimately, the thing to remember is that gold really wants to be free. All we need to do is help it a little! MBT Eric

[Geo-George]

I figure about 30/35 gpm for my "Tom".
Material is classified down to 1/8" minus before I run it.

[jmcallister]

Just curious what size mesh gold you get with your dredges? Typically a pan can get down to 200 mesh.

[pickaxe]

I generally get gold in some quantity of sub-100 mesh range, to as small as the eye can see. Stuff is a pain to collect.

[DJR]

It's too cold to talk about dredging, stay home drink lots of booze. Or better yet go to a friends house drink their booze.