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Fine gold on an dredge


#1

looking at an claim that has super fine gold. running an 5 inch keene at the mo but might go to an trommel if need be. what do others do to get the super fine gold thanks


#2

adjust your table widen your box and use different matting


#3

Hey there
Is your dredge a 3 stage box? If so what you want to do it ensure your power jet is slid as far back out of the the flare as possible. The reasoning behind this is it creates a longer area after the jet log for fine gold to stratify in the flare. The idea here is by the time the gold hits the first stage of the box it will be caught in the first set of riffles. Also you want to ensure your angle of the flare is quite steep. What this will do is allow the water to “well up” into the box with lower turbulence. The key to fine gold recovery is reduce turbulence and classification…

The other thing you want to do is get hold of Dan @ dredge NZ and purchase a new woven wire classifier from Keene to replace the punch plate classifier into your 3rd stage. The woven wire has a greater surface area and also creates more of a drag on the water column in the dredge. This will ensure more water enters the bottom stage as well as getting more of the gold to enter the bottom stage. Once its in the bottom stage even the finest gold isn’t going anywhere.

The idea of putting mats in ones dredge is debatable. A dredge sluice is a way different beast to a river or high banker sluice. My thoughts on the gold hog matting for a larger dredge such as yours are they are just a marketing ploy as the volume and depth of the water column and lack of ability to radically change the sluice pitch in a dredge does not lend itself to the philosophy of how the mats work.

The other thing you want to do is on your 2nd stage is look at removing some of the larger Hungarians riffles and replace with heavy expanded metal. Ill post a pic of what mods ive done with my 2 stage and it might give you some ideas. This was developed by Keene and they now sell this upgrade. Once again talk to Dan.The reasoning behind this is the large Hungarians riffles are really good at capturing nuggety gold but create to much turbulence for very fine gold to settle.

Also when your in fine gold area reduce your rpm down on your pumps. This will be a trade off with a slight increase in blockages. Try and run your sluice box with a slight angle as well with the choke to the bottom stage wide open.

And if you do decide to upgrade and get another dredge dont get a Proline for fine gold. The Prolines are an awesome dredge and shit over the Keene’s in some ways. Unfortunately when it comes to fine gold recovery they just dont compare to the Keene 3 stage box (if setup properly) . A 3 stage box on a Proline dredge would be an great machine. I’ve seen this done before when I helped dredge with another bloke on the Marawhenwa River at danseys pass with a 5 inch proline running a 3 stage Keene box.


#4

As you can see there is a classifier over the large raised expanded. This helps with fine gold recovery


#5

This is with classifier removed. Matting under neath is miracle matting which I have replaced with Keene carpet


#6

As you can see the punch plate to the 3 stage has been replaced with woven wire. Notice the increase in area for greater water flow into bottom stage as well as each woven wire thread acting like a mini riffle for fine gold


#7

Sound advice there prich , I tryed a classifier over my back / top section a few years ago but for some reason it wouldn’t work , mite ditch the riffles & see if the expanded mesh works better.cheers


#8

use both all the more the better the catch


#9

Hey sooty - yeah the issue with small size woven wire over those big Hungerians you talk about is they do such a good job of slowing the water down they actually cause a collapse of the vortex created by the riffle. This results in the riffle packing up and gold migration down the sluice.

That’s why the use of raised expanded metal under small woven wire is so effective as these types of small riffles work well in conditions where water flow is slow and less affected by surges in water flow. This is a perfect environment for fine gold to be captured.


#10

Need to trim the fine woven wire back to expose the 1st Hungarian riffle otherwise it just chokes up i found


#11

to capture fine gold, you need to move your fine gold slurry to a low turbulence area where the fine gold can settle into appropriate traps. Hi turbulent areas in rivers usually do not yield a lot of fine gold. I am currently thinking of modifications that will achieve good results with my dredge, which will be tested this summer, after which, my results may be revealed.