New Zealand Gold Prospecting & Metal Detecting Forums Archive

I am sure that a lot of members will be able to chime/wade into this subject with "Gusto"and come to the party with lots of fors and againsts for every type of system as to its worthiness of saving gold, whether it be fine or of larger sizes.

The in and outs of this age old method of segregation of the golden particles from riverbed gravels involves many, many factors for successful separation.
These factors need to be taken into consideration with some seriousness if you wish to save most of the gold that goes through your sluice of choice, because you have spent some sweat and maybe some tears in getting those gravels into the header box of your sluice! only to sometimes, have a considerable part of the gold that you should have saved go hurtling through the sluice, once more be free to continue its journey to the sea

The factors which seem to rule in the sluicing world appear to be things like:
Strengths and depths of water flows--amounts of loading and speeds of gravel flow within the box-- sizes, types, and spacing of the riffles--length and depth of the sluice itself--angle of attack of the sluice box upon the water that courses down its channels.

As regards this last--a fairly good rule of the thumb, seem to be to set your sluice up originally with a slope drop at the bottom end, of around 30 cm, in a sluice of 150 cm in length.
This general start up position, can then be adjusted to try to suit the size of the gravels that you wish to put through, taking into consideration how much water supply that you can tap into, and whether you wish to rush them through, or process them in a more slower leisurely manner that’s conducive to saving the finer particles of gold which always exist within any gravel bank in a gold bearing country’s waterways.

This setting up of the sluice should be done so that the gavels that pass down its channel are in a constant state of “Agitation”, just as if there was a ”Slurry” of material composed of rocks/sands and mud traveling down its channel, churning and tumbling along as it goes.
If this angle of drop is set to achieve a good recovery of gold, this will be noticed by the sands and gravels that settle behind the riffles being in constant motion.
“Don’t be fooled by seeing only the top portion of these concentrates bubbling up and down“,

“Try to make sure that the whole component of stuff that’s caught behind the riffles is in movement from top to bottom”
This movement not only helps keep the riffles clear and un-hard packed with your caught concentrates, but the gold bits are more likely to settle to the very bottom of the sluice base if everything is in constant motion, instead of some of the gold skidding over any hard pack sands and stuff, (Which it will do.) and becoming lost out of the end of your sluice.

Even in a river, Gold needs the gravels and rocks etc, to be in constant movement for it to be able to settle through them to the bottom of the river.
If the bottom was always like a tar sealed state highway, the gold would be traveling in the fast lane when the river was in flood, only settling out as the water slowed down to a near zero stop
O.K. fellers and gals, I am sure that there is much more to this process than I have touched upon, as I am not up to speed with all the latest methods of gold recovery by all these fancy and lightweight sluices that we have at our disposal today.

A good point of interest in the above respects, is that in the old days, the miners used an appliance called a “Rocker Box” which I’m sure that you are all familiar with its operation. But just in case! It was like a sluice box sitting on curved legs,(Sort of like a baby’s cradle for rocking them to sleep,) this rocking action kept the gravels in constant motion, and settled the gold out very successfully.
Not bad for an old method of doing this ehh!

Anyway, read and forget, or make a comment of your own, I’m sure others would be interested in your thoughts and methods of achieving this important end in any gold saving adventure.

Cheers---Colin.

Sizes of riffles, and the speed or volumes of water that you put through your sluice?

It's always appeared that the size,and the height, or the shapes of your riffles can control the amount and and speed, and also catching capabilities of the riffles, due to the amount of the water current that you send through your sluice.

If your riffles are short, the current has to be adjusted to a fairly mild and to a slow enough flow to cater for the smaller riffles catching capabilities, as if its not, then a lot of gold could/will just get washed over them before it has any sort of chance to settle, and get caught behind them.

If your riffles are taller, then you can increase the water currents force and amount to send the gravels through faster, therefore hopefully saving time, and more hopefully still saving all? The gold that passes through the sluice.

Recessed riffles/ ruffles like those that seem to be a feature of modern light weight ABS type sluices, seem to work well, due to the fact that they do not present any obstructions to the waters flow, but be aware that if you send lots of fast water through them hoping to speed things up, then your kidding yourself, and will be disappointed at the end of a run with your gold returns. It is my opinion that the rule to use with these apparatuses, is to operate them in a slow and, “Steady as she goes” attitude.

In all my experiences of the many years that I spent trying out and experimenting with many different sluice designs, plus water flows through them, using all sorts of media for riffles, manufactured types, or just what was available at the time/site, sticks, stones, grasses, mosses, and also the barks of trees etc. ( I found “Punga” root systems, cut into roughly sluice box width blocks excellent for catching all sizes of gold.)( If it was there of course!)
Also, in the old days, I found that the savings in Backpack weight by using natural things that were available to hand on site, worked pretty good for me.
Just remember that a river does not have access to “Manufactured” sluice boxes, it does the separation processing of gold pretty bloody well with what’s available to it in its river bed.

In respect of all the above crap, there is one item that I always used on any sluice I used, and of which I have “Never seen or heard mentioned”, ( even on the Internet.) as to this secret? addition being of so much use to a sluice setup, and also as to being a very helpful thing/gadget to attach to your sluice, as it sort of did away with most of the classification of sizes of your gravels!
And that’s got to be a Bonus in this game. With this addition you could practically send the whole river load of water hurtling down your sluice "Hollas-Bollas", and still concentrate the gold.

Anyway, that’s it for now, feel free to criticize any points that you don’t agree with, as this makes the whole purpose of the forum worthwhile. ( To me anyway. : ) : ) : )

Cheers and regards---Colin.

thanks for your post about sluicing just got back from west coast found a few colour so set up my sluice box started digging came to wash up bugger all so must have done something worng came home saw your post so keen to go back a try again . thanks cavey

"Hey Cavey".

Dont take my measurements of a drop of 30cm in 150cm length sluice as Gospel.
This is o.k. for larger stuff, but is a bit steep for fine golds.

Use the size of your (screened) gravels as a guide, and watch their "Jitterbugging" behaviour within the sluice confines, adjusting the waterflow and/or the slope as required.

This means: "Use your initative to achieve your end goal.)

Cheers---Colin.

I'm thinking a piece of the coarsest astro-turf you can buy would be good for the the end of the sluice to just sit on. That way, you have a chance of picking up some of the finer gold that may have gone through.

i thought i would post a picture of my flared sluicebox.


unfortunately i can't seem to do so. can anyone help on this?

maybe this site needs a questions and answers section for site related issues.

i have tried clicking the 'insert image' button, and also have clicked the 'attach files to this post' box. neither worked?


anyway i will try and describe the sluicebox and hopefully the image will follow shortly

i think the sluice is called a "prospectors choice". i bought it from Miners Den in victoria, australia. i ordered it over the internet but i'm sure they would also do phone orders. just need a credit card.

i think i paid $180+freight several years ago. price has gone up a bit now.

at the time i was a bit hesitant to buy one and it was a bit of outlay and i always used to build my own from scrap of wood and metal.

looking back its all a bit of a laugh really. i remember one that i took up the arrow on a stinking hot day. made of roofing scrap with wood riffles i left in up there as it got so bloody heavy when wet.

buying a box was really the best move. these guys have been refining their product for years. there are good weight savings, they are ergonomic to carry, usually with a built in sturdy handle, and most importantly they are quick to disassemble to clean out the concentrate.

my box has a flare. apart from being a bit of extra hassle when walking i never don't use the flare (it can detach if needed). the flare means you can gather water to feed the box in pretty low flows. yet the box still handles water velocity that rips rock and stone thru it and still recovers good gold.

the box came with legs as well. these i don't really use but i could see them being really useful if you only head out ocassionally. basically the legs allow you to easily adjust the bottom height of the box up or down so once you have the top of the box right for water inflow you just slide the legs up or down and tighten in place with the wingnuts. this allows you to get the fall right to let you get the stone tumbling through. so say you start putting sandy material thru you won't need much fall. if you part way thru you work start putting bigger material thru all you need to do is drop the legs down a bit and the velocity increases.

the box has a common type of boat carpet. this has grooves in it to catch the gold which it does well with all size pieces. the carpet is held in place by the hungarian riffles. these work a hell of a lot better than sticks or bits of wood. as they are on an angle they create the perfect flow of water over them, any any gold passing over them drops out underneath the riffle.

i have never seen any gold make it past the third riffle. as a check to see whether any gold is being lost i test the sluiceboxes tailings every now and then also.

the only thing this box doesn't have is black ribbed matting. several people have mentioned this to me as an upgrade but i feel it works fine as it is. black matting definitely makes it easy to monitor each shovel of dirt for gold but i feel if you know your sluicebox you can get to know where signs of gold show anyway. if the flow is right and you put some material at the lip of the flare where it enters the straight part of the sluice you should see the dirt and stone slowly suck away leaving behind and flakes to see.

upon end of day cleanup i simply undo the wingnut at the bottom of the sluice which releases the riffles (the top end sits under a couple of nuts which holds it down against the carpet so no worries about it not secured down enough - my old handmade sluices often got bashed about a bit and ended up letting a bit of dirt underneath the carpet i suspect). out comes the carpet which i carefully roll up and dump into a bucket of water to transfer later to a pan.

i have never failed to get gold with this sluice. its taking several years punishment including use in large rivers and its still going strong.

hopefully i can get a photo of this sluice up so you can see it.

Hey Simon, I don't know what's up with the file attaching thing, maybe Gavin can help, or you could open a photobucket account and use the photo URL on your photobucket account to post on here.
Good luck

Tried out my plastic california sluice box for the first time the other day in Coro [at the top of the Maratoto trail up behind Waihi]. Was more concerned with getting a feel for the loaded pack on a good 2 hour tramp than finding gold. On the way back to my sister's farm got slightly lost on the connecting trail and ended up doing the hard yards for a while down the head waters of the stream that leads to their farm. Lots of supplejack and trees to navigate.... had to take the pack off and throw it through at times... and the sluice box... lucky it was plastic! Climbed out to farmland when I saw some daylight to the left at the top of the bank. Phew.

Bought some army supplies in Welly today, catching the ferry over to Picton tomorrow, and hope to park the camper up somewhere around the Wakamarina. If anyone's keen to meet up for a day's fossicking anytime soon, feel free to send me a PM! I'm planning to spend the next few months cruising about the top of the South Island looking for the yellow.

Roman.