Hi. I’m Jason Kincade,
The sluice box is a tried and true invention that has been employed by placer miners from antiquity to the present day to separate and capture a high percentage of gold from auriferous (gold bearing) gravels, while increasing production over slower methods, such as the gold pan and rocker.
When I first started sluicing, years ago, I used to agonize over setting the proper slope to the box. I was constantly readjusting the angle… attempting to achieve optimal conditions for gold recovery, and I always doubted my tweaks. There were so many obvious variables to consider; it was frustrating and seemingly complicated. However, as you will agree after reading this article, it really isn’t difficult at all, in fact, it’s a very simple procedure to perfect.
As you probably already know… the best-designed Hand-sluices on the market today are constructed of aluminum, resembling the one shown below. I prefer them for small operations over the heavy, wooden, handmade variety, mainly because they are efficient, compact, durable, inexpensive, and best of all, light and much easier to pack into remote locations. Notice the ‘handy’ handle on the model pictured below.
However, if you’ve got your mind made up to build your own sluice box… look over this book of plans.
Undeniably, one of the most important considerations when setting up your sluice, is the slope given to the box. That angle will influence the auriferous (gold bearing) material’s speed of travel through the box and, therefore, the degree and efficiency of tumbling, segregation and settling of the ‘heavies’, and expulsion of waste (tailings).
The optimal slope or angle to be used will be contingent on:
(1.) The size and density of the material to be processed.
It should be no surprise that denser, larger materials require a somewhat steeper slope. Classifying (screening) the material before processing through the sluice will eliminate the oversize gravel and allow for a shallower slope to the box. Less water flow will be needed, and there can be no argument that classified material will run smoother and yield a higher percentage of recovery. However, for a one-man operation, classifying is time consuming and not always the most efficient or practical approach. Obviously, if you do not classify, hand removal of the bigger gravels that get hung up in your box will be necessary.
Naturally, I eliminated the ‘jumbo’ rocks by hand as I filled my bucket with gravels preparatory to loading my sluice, but I seldom screened because not doing so allowed me to process a greater volume of material, and comparison testing, in most cases proved, to my satisfaction, that it more than made up for what little gold I lost in my tailings by feeding unclassified gravels through my sluice. However, screening is a personal choice, and for many proponents it’s the only way to go.
(2.) The volume of water available to be directed through your sluice box.
It’s important not to run the water so slow and deep through your box as to hinder the crucial eddy effect of the riffles; ‘rippling’ of water above the riffles is a must!
If the flow of the stream is fast in the section where you’re setting up operations, the slope of your box will not need to be set as steep to achieve optimization as it would in a slower moving section of the stream. Other factors, such as riffle design, influence the required flow and therefore the optimal slope… but let’s keep it simple.
If I were you, I wouldn’t get hung up on the single, ‘best’ angle at which to always set your sluice box, because the optimal slope stetting must be changed and adapted to the conditions at each new location where you setup operations. Let’s face it, setting the box’s optimal angle is not rocket science; no, it’s determined by simple observation.
Start with a slope of what you estimate to be about one inch drop for each foot of box (The intake of a four foot long sluice box would be set approximately four inches above the level of the discharge end).
Adjustments are likely to be required based on the available flow of water and the nature of the materials to be fed through the box. But there’s no need to get all techie, such as with a level and tape measure; just relax and estimate the slope… (eyeball it). Remember, every tool you pack in, you’ll have to pack out!
As you feed a charge of material into the front, flared end of the sluice, time how long it takes most of the sand and gravel to clear the matting behind the first riffle; a few pebbles and rocks may linger along with some high-density materials such as lead, nails, black sand, and gold (if present), and that’s a good thing… exactly what you want.
As a general rule, if the process takes more than fifteen seconds, but less than forty-five…you’re in what I call the Recovery Zone (your box angle is set within limits that favor gold recovery). Within those general (but not immutable) boundaries, you’ll have to decide if more or less angle is called for based on yardage expectations, the size and consistency of the material you’re running (Are clay and mud balls or other special considerations a factor?), the panning results from your tailings…and good old miner’s intuition.
After each change in the slope of your box (during your early learning stage), retest to confirm that you’re operating within the ‘Recovery Zone’. It may take awhile for you to achieve total, unshakeable confidence in your setup technique, but trust me, it will become second nature with just a little time and experience.
To test your competence and boost your confidence…count some bird shot, or BBs (ten or more), and mix them into your material prior to a run of an hour or so. If during clean up, you recover all of your shot…you can be assured you’re not loosing much gold.
Of course, when you’re setup and running for maximum production, there’s always going to be that inevitable percentage of the very finest of gold (the flower) that will slide through your system and be lost in the tails… like a fart in the wind. But don’t stress over it and stem the flow, just let it go…like the old timers did. Because, as they well knew, if the aim is to make money sluicing… production is king!
In fact, when you have a large volume of ‘marginal’ gravels to run through your sluice box (as is commonly the case), testing may prove that steepening the slope of your box could significantly improve your recovery, per unit of time and labor invested, by retaining more gold from the added volume of gravel run through the box than what is lost due to the increased processing speed. Inevitably it comes down to a judgement call, based on one’s priorities.
On the other hand, when you get into a rich streak, especially one carrying a large percentage of fines (fly specks and flower gold), adjustments to your process will be in order; lessening the slope and the water flow and classifying the material before the run might well be in your best interest. It’s another judgment call that, with a little experience, you’ll soon feel confident in making. Just use your ‘gray-matter’…sluice smart, and you will greatly increase your chances of success.
I found this short video on YouTube and embedded it here to give you a chance to watch one man’s sluice box setup and production technique.
Good luck! I hope to see ya in the field.
Now don’t just ‘hit’ and run… that ain’t neighborly! Before you split, be sure to Leave a comment
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{ 6 comments… read them below or add one }
what if i am trying to catch flour gold?
and magnetics are removed after flour size classification?
Mac-
I’m not the most qualified guy in our hobby/profession to address your questions. I have had but precious little success trapping a respectable percentage of flower gold in my sluice box operations. Testing my tails, as I regularly did, proved to me that much of the flower gold that I encountered was lost… back into the river. A significant percentage of those minute, pesky particles floated on the surface or were pushed along through the box by the current.
Some will disagree with my technique, but I didn’t consider what little I was loosing in flower gold during my hand sluicing days justified setting my sluice at the optimum angle and flow rate for its efficient recovery, simply because it would have cost me too much in overall gold production over the long-run. Of course, if I had discovered a rich deposit (high percentage) of flower gold… that would have been a whole different matter. I would definitely have screened all my material through a grizzly prior to sluicing, adjusted the angle of the box to optimize the flow of water, considered introducing mercury into the box, as well as adding width and length to its run. I also would have looked into the feasibility of investing in a more efficient flower gold recovery process.
As for the separation of magnetic particles, primarily magnetite and hematite, from concentrates in the placers I worked (in which flower gold was never a significant constituent)… after plucking out the ‘pickers’, I panned my sluice box cleanup material down to fine, black sands. Then I dried them (the concentrates) either in the sun, or on a stove or campfire, after which I removed most of the magnetic sands with a magnet before separating the remaining ‘heavies’ from my gold by using a handmade blow box. That was low tech and worked fine for the relatively small quantities of gold and black sands that I accumulated daily. But, when I was dredging, and filling buckets and buckets with heavy black sands, I found that mechanical gold wheels… used to separate the fine gold from the heavy volume of concentrates… worked really well.
Separating gold from concentrates is an art that deserves a lot more attention than I can provide here in this necessarily limited response to your comment… something I’ll address in detail, in a dedicated post, one of these days.
With a little luck, someone reading your question, someone having more experience with sluicing for and cleaning-up flower gold than I, will be kind enough to give you, me, and all else who are interested, some valuable tips… here in a comment. Sorry I couldn’t have been of more help.
Good luck,
Jason
this is great. I take the same thing holds true with a dredge?
I what to put A beeZee Screen(wedge wire screen) starting about 1/3 down the sluice and run about 12 in then continue on with a layer moss Corrugated vinyl and expanded metal ( the moss i am not sold on yet it seems to hinder more than help, but who am I) But if the flower floats over the top then its a matter of flow and more time for the gold to drop. Would this be correct?
Michael-
In your first comment, you asked: “I take the same thing holds true with a dredge?”
If you’re asking about the flow rate and angle settings of the box on a dredge needing to be ‘tweaked’ (as is the case with a standard hand-sluice) if your primary focus is to most efficiently process and capture a high percentage of flower gold, then I would say yes. Seems to me a sluice box is a sluice box and flower gold is flower gold… no matter where the two shall ‘dance’.
And, as to your observation in your second comment: “But if the flower floats over the top then it’s a matter of flow and more time for the gold to drop.” I think you’re partially correct. I say partially, because, not all flower gold, or even most of it that is lost, is lost because of a propensity to float. Therefore, other factors (negative influences) are in play and may need to be resolved… depending upon how much of the flower you are determined to capture and how “techie” you’re willing to get in order to capture it.
It is a complex problem, and I should reiterate at this juncture: I definitely (and regrettably) am not an expert on flower gold recovery… especially if we are talking about shoveling bank run placer materials through a sluice box… in the field. So, take what I have said with the proverbial grain of salt.
I’m interested in solutions too, and I’m still hoping for a ‘real’ expert to drop by and set us all straight. In the meantime, here are some links to check out. They’re not definitive, but I hope they help… at least a tad.
1) An online forum discussion on Recovery of fine floating gold.
2) A short online Floating Gold Tutorial
3) Sluicing and highbanking for flower gold on YouTube
Good luck. Come back and let us know how you make out with your box design.
Jason