A few newbee questions about sluicing

[baggerman]

I don't post here often but read quite a bit. I just got back from 3 days of sluicing (about a 3' sluice) for the first time in my life and have a few questions.

1) I classified my material to 1/4" before running it through the sluice but it still seems like I have quite a few smaller pebbles. Should the material be classified further or is this about right?

2) How much should I feed the sluice? I never let the material get above the first 1 or 2 aluminum riffels.

3) How often should I clean the sluice out into my bucket?

4) What is the best way to get the real fine flour out of the black sand?

I panned out a handfull from the first sluice cleaning and got quite a bit of black sand and a few very small specks of color. I now have about 1/3 of a 5 gallon bucket to go through.

 

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[Jeffro]

I don't post here often but read quite a bit. I just got back from 3 days of sluicing (about a 3' sluice) for the first time in my life and have a few questions.

1) I classified my material to 1/4" before running it through the sluice but it still seems like I have quite a few smaller pebbles. Should the material be classified further or is this about right?

1/4 inch screen is plenty fine.

2) How much should I feed the sluice? I never let the material get above the first 1 or 2 aluminum riffels.

As much as it'll handle without fillling up the space between the riffles. If less than half the carpet is showing between riffles, slow down a bit on feeding your material.

3) How often should I clean the sluice out into my bucket?

Depends from stream to stream. If you see black sand packing the upper third of the riffles, it's probably time to clean it out. Could be once an hour or once a day, depending on your area.

4) What is the best way to get the real fine flour out of the black sand?

Several good screenings and a wheel. Run each screening seperately. Pan anything larger than 1/8 inch. There are plenty of other methods, but this one will get the most out if done properly, in my experience.

I panned out a handfull from the first sluice cleaning and got quite a bit of black sand and a few very small specks of color. I now have about 1/3 of a 5 gallon bucket to go through.

Should go pretty quick, sounds like.

 

[twobobs]

Thanks for your post and the reply. I'm new to the forum and to prospecting. I recently built a recirculating sluice from scrap aluminum and stainless. I'm hoping that someone will give me some guidence on the setup. The problem i'm having is a build up of rocks and gravel in front of the riffles. The first slope has a 1/2" grate so the larger rocks slide off the end before they reach the riffles. The first two riffles are 3/8" high and then the remaining 3 riffles are 1/4" high. The overall length of the riffle section is 2 feet and the width is 6 inches. The slope of the riffles is 1" drop per 12" of length. My water pump is 370 gallons per hour. The water is distributed through twelve 1/8" holes.

The flow seems good but the backup is pretty severe. It helps to shake the sluice section side to side or use my hand to help the material through the riffles. How does all this sound to you pros? Should I get a bigger pump or reduce the riffle height? Plan on using this in the Arizona desert and in Northern California.

 

[Goodyguy]

I don't post here often but read quite a bit. I just got back from 3 days of sluicing (about a 3' sluice) for the first time in my life and have a few questions.

1) I classified my material to 1/4" before running it through the sluice but it still seems like I have quite a few smaller pebbles. Should the material be classified further or is this about right?

2) How much should I feed the sluice? I never let the material get above the first 1 or 2 aluminum riffels.

3) How often should I clean the sluice out into my bucket?

4) What is the best way to get the real fine flour out of the black sand?

I panned out a handfull from the first sluice cleaning and got quite a bit of black sand and a few very small specks of color. I now have about 1/3 of a 5 gallon bucket to go through.

I would have to see it in operation to fine tune it. Fine tuning requires adjusting the angle of the sluice box and adjusting the water flow. Fine tuning also depends upon the type and consistency of the material being processed.

This is something you will have to get the feel of through trial and error. Unless you have an experienced prospector nearby to offer their help.

It sounds to me like you are on the right track the riffle height is fine. 1" drop to the foot is ok as well. If you have a way to control the water flow (speed and volume) adjust it until you conform to Jeffro's advice. You can get some small pieces of lead and test catching them in your moss, count them first so you know how many you have, then back off your flow until you catch them all. Or speed up your flow until you start to lose some then back off until you don't lose any.

If you are not able to see a little white water going over the riffles ( the water should appear to be hopping) then you have to either increase the flow or increase the drop of the sluice. A weak water flow will have to be compensated for by an increased drop of the sluice. If you have to go more than 2" to the foot of drop then you need to find a way to increase the water flow or you will be losing gold.

Feeding your sluice too fast is the main cause of clogged riffles.

GG~

 

[baggerman]

I too want to say thanks for the reply. I was also having some of the same issues with build up on the downstream side of the riffels. I tried getting more and less water which didn't seem to make a huge difference so I used a stick to move the gravel around every so often. Do I understand correctly that the sluice should have about 1" of water in it and about 1" drop for every foot in length? I have ALOT to learn but must say I really enjoyed myself.

 

[Goodyguy]

I too want to say thanks for the reply. I was also having some of the same issues with build up on the downstream side of the riffles. I tried getting more and less water which didn't seem to make a huge difference so I used a stick to move the gravel around every so often. Do I understand correctly that the sluice should have about 1" of water in it and about 1" drop for every foot in length? I have ALOT to learn but must say I really enjoyed myself.

Everybody gets some build up on the downside of the riffles. If you don't, then chances are you are losing precious gold!
I stop every so often and clear the riffles if too much build up is occurring. The water flow should be fast enough to see some white water going over each riffle. But I guess that depends on the design of your particular sluice. Clogged riffles could also be caused from feeding material in too fast. Give it a chance to wash down before adding more.

Maybe the term "white water" is the wrong description. You want a depth where you can see the water slightly jumping over the riffles. It should not be a smooth stream of water, but hopping some. That's about it. Practice is the key


GG~

 

[Jeffro]

I'm just the opposite, I like to see my water plenty deep in the sluice. No white water over riffles. Just a preference I guess.

Bobs- you may want to enlarge the holes to get more water, sounds like. And point them towards the back, not towards the riffles. I'm assuming you have the upper end of the sluice blocked for recirculating? Like Goody said, its tough to guess without seeing what is going on in real life. I'd suggest playing with your sluice setup in a stream where you can get plenty of water and try different things until you get a feel for slope and water flow. try BB's or little lead shot like Goody suggested. It's all about testing and practicing until you get a feel for it. Then try and replicate the same effect in your recirculating sluice.

And Bagger- the 1" drop is just a rule of thumb. An average to adjust from. Don't consider it a hard and fast rule. Play with it until you get good flow and the buildup isn't so bad.

 

[Hoser John]

6 gal/min pump is not a sluice--thats a highbanker and NOT ENOUGH WATER TO DO SQUAT WITH!! John

 

[Goodyguy]

6 gal/min pump is not a sluice--thats a highbanker and NOT ENOUGH WATER TO DO SQUAT WITH!! John

John remember TwoBobs box is only 2 feet long by 6 inches wide. And the riffles are only 3/8" and 1/4" high. I would say that may not be enough flow even for such a small sluice.

If you are not getting enough flow then perhaps a higher capacity pump is in order. You do not want any shorter riffles than you already have.

I think what you have built would be good for running your concentrates through before panning, or using a spiral wheel for final clean up. however I suggest a much larger unit for any serious sluicing of raw material.

GG~

 

[baggerman]

And Bagger- the 1" drop is just a rule of thumb. An average to adjust from. Don't consider it a hard and fast rule. Play with it until you get good flow and the buildup isn't so bad.

That's kind of what I figured so I tried to use this as my starting point and think things went well for my first time out. If you wouldn't mind a newbee tag along the next time you go out send me a PM as I live in Corvallis.

 

[Jeffro]

Sure thing Bagger- Only I wouldn't count on me being able to find this post again when the time comes, LOL! Can you send me an e-mail from my profile? I'll have a way to contact ya then.

 

[beaks]

you need at least 850 gph to 1200 gph to unload the riffles and create a good vortex on a 3'x10" sluice and a good magnet to clean the magnetics from your riffles while sluicing(they sell them on ebay)

 

[baggerman]

you need at least 850 gph to 1200 gph to unload the riffles and create a good vortex on a 3'x10" sluice and a good magnet to clean the magnetics from your riffles while sluicing(they sell them on ebay)

Thanks I'm going back out in about 3 weeks and see if I can make use of some of the info here. There was alot of black sand in what I brought home and read somewhere that there can be quite a bit of fine goild in the black sand. Does any of this fine gold get trapped and picked up with the magnet?

 

[russau]

yes the fine gold will get encapsulated by the B.S. andif youll let it dry out and crush it youll see a lot more fine gold. the GPAA has a neat video of ralph Yeager and his black sand operation and i think youll benifit by veiwing it. it was rerun last weekend on the outdoor channel or you can order it from www.goldprospectors.org and look around the home page for videos.

 

[kiwi jw]

G'day Twobobs, If you are getting build up infront of your riffles & it isnt clearing then your water flow/velocity is not enough &/or your riffles are too high. The size of your box (length & width) will determine the height & spacings of the riffles & the velocity of water you put down it. A short box needs smaller riffles (height), precalssified material so the smaller riffles can cope with it & just enough water flow to wash the material through. Otherwise you will lose gold. There should be a dancing, vibrating, shuffling action of the material between the riffles. This causes the heavy elements to sink through the material & shuffle up behind the down stream side of the riffles while the lighter material ends up dancing on down & out the box. The right water velocity & action behind the riffles is determined by amount of flow & steepness of the box. You need to get this right before you start shoveling material through in earnest. Just play around with box slope & amount of water until you get that shuffling action between the riffles & you will be set.
A bigger box will handle bigger riffles & bigger material & faster water, but again you really only want enough water flow to wash the material through. Too fast & you will lose gold.

You will see here that this little stream is only piddling water yet these riffles were coping as I preclassified the material to 10mm & less. The secret is to not over load the box & riffles, but let the water do the work. In this case I had to feed it pretty slow due to the small amount of water. As it was I had the entire creek flow going through.

But I found some nice gold

Happy golding

Kiwi JW

 

[rwells]

I got some good info from this post, but have a couple questions. Are al riffles ok or will rocks wear them down. I am building a 36 X 10 inch sluice. Water supply is coming from a 2" dredge. What height should the riffles be? Thanks in advance

Rick

 

[Goodyguy]

I got some good info from this post, but have a couple questions. Are all riffles ok or will rocks wear them down. I am building a 36 X 10 inch sluice. Water supply is coming from a 2" dredge. What height should the riffles be? Thanks in advance

Rick

I would say between 15/16 of an inch to 1-1/8 inch for 36" x 10" box supplied by 2" pump. The taller you go the faster the water flow needs to be. Typically a dredge will supply water faster than a high banker needing a slightly taller riffle than a regular sluice.

Experiments corroborate published data that in a sluice box the ideal ratio of the height of the riffles to the riffle spacing should be 1:3.5. If, for example, the riffle height is one inch, then the riffles should be three and one-half inches apart.

Ask 10 prospectors and get 10 different answers.

Maybe call or e-mail Keene eng. and ask.

[email protected]
Keene Engineering
Outside of California - (800) 841-7833
Inside California - (800) 392-4653


GG~

 

[Jeffro]

No matter what size sluice- I really like expanded metal for riffles. Smaller and thinner for small sluices, but large for larger.... Get the kind that is not flattened. Some people call it "armor weave" and it comes in varying gauges and spacing. Tack it to your side bars just like you would regular riffles and your good to go. Water flow is less of an issue with these things installed.

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[Goodyguy]

Good point Jeffro, I was assuming the riffles were going on top.

I use ribbed rubber mat on bottom then nomad (miners moss) on top of that then the expanded metal then the riffles on top of the expanded metal.

GG~

 

[Jeffro]

Good point Jeffro, I was assuming the riffles were going on top.

I use ribbed rubber mat on bottom then nomad (miners moss) on top of that then the expanded metal then the riffles on top of the expanded metal.

GG~

My Keenes are set up that way, but most of my homemade stuff is sans riffles. The expanded metal IS the riffles. Very little water to run one, and it helps break up clumps pretty good. I work in sheet metal so i have an unending supply of this stuff, but it is available for most anybody at any scrap metal yard. Also online.