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Gold Hog - Riffle Shapes and Angles

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Riffle shapes, sizes, styles, angles.....

What you’ve been waiting for right?
Maybe or maybe not. Take a look at the shapes below. They are just a few of the MANY we tested. Which ones do you think performed the best?

Here’s where we tell you information you might not like. They ALL did their job pretty much. Here’s a funny note. We also tried bricks and tree branches in our sluice just to make a point. They ALSO captured gold, so it’s NOT rocket science. 
Why did they all work? Because the job of a riffle is simple if you have been READING and understanding our point.

The job of a riffle is simple. 
1) Interrupt the flow of the MIX.
2) Cause that interrupted level of the mix to go over the riffle.
3) End in a manner, have a shape, that causes a vortex and a drop off.
4) Create a “low flow zone”, behind the riffle, that is out of the main current’s velocity offering a CHANCE for gold recovery / storage.

Now… here comes the HARD PART, and HERE is where ALL the debate begins.
What do you want the “working zone”, area behind the riffle, to look like?
If you comprehended our previous findings, you’ll understand that you’ll want a riffle with limited “launch” but a good strong vortex.    Your “riffle zone” should actually be a somewhat turbulent area that is constantly working and scrubbing.  We think the biggest mistake prospectors make is “quieting down” the riffle zone too much.  Much of this “quieting down” behavior or “movement” has come to age with new recovery and finishing equipment that helps extract VERY fine gold.
We keep seeing new BIGGER, LONGER, more gentle slope riffles, all claiming to hold “more gold” when in fact the opposite is probably happening.  They are collecting more “material” but usually not more gold.

Since many did their job well, let’s point out the ones that did a poor job, based on what we told you earlier, which is the job of the riffle. 

Riffle “D”: This style was did NOT interrupt the flow enough, and would often turn into a “launching ramp” that threw gold over the vortex with no slow down action.

Riffle “I”: This riffle interrupted flow, but very little vortex was present and often unstable. Became easily filled with light material.

Riffle "E" was actually one of best performers. Something about the double ramp and Clarkson-Like top, made this one a great riffle.  

Size of the riffle…

Again, there are a TON of variants that influence this decision for you.
Let us summarize, offer our suggestions and thoughts FIRST, and then explain.
Size will need to be increased slightly based on water flow and depth of water in box. However, keep in mind that we are working WHAT LAYER.... The bottom layer, correct. So, as long as the bottom layer is being worked, we find that the riffle needs to be no larger.
Also, if you are working at lower flow rates, such as a stream sluice, you will find it more challenging to clear larger riffles. Therefore you might have to increase your pitch. 
We are seeing more and more sluices going to expanded metal only, but we do like to see at least a PORTION of the box have SOME scrubbing area. (Hence the creation of our Wild Boar Scrubber mat.) Breaking up clay, dirt, and general material is an important part of the recovery process.


Water speed / velocity, angle / pitch of the sluice box, amount of water / water depth in sluice.

Why would we LUMP all of this together?
Because in a way, it all works together and has the same impact “across the board” on all riffles, boxes, and behaviors.  It will change the way your box works, riffles work, the amount of material you hold, speed of the water and vortexes , the amount of material held behind riffle, etc, etc.
We will “generalize” here a bit to keep this section from being 10 pages by itself.
First, what happens and why most people CHANGE it.
Let’s say you’re running box with a 1” by 12” pitch. (For every foot of sluice box you have 1” of drop.) So your water is moving 3mph through the box (just picked a number out of thin air) and you have too many rocks and material building up.   So, you drop your box to a 2” by 12” pitch. Now your water speed is increased to 5mph and the HILL is steeper allowing rocks to ROLL more freely.  “That’s better, good clearing.”  That, in a nutshell, is what we see in the field.  Same with water flow.  Box not clearing properly??? , increase the water flow and… “Yeah, baby, now we’re cooking with gas.”
Believe it or not, this “Kentucky Windage” is the proper method in the field.  While setting up, run material through your box.  Make sure it is level. (Side to Side) Then run material at the same rate you will be working it.  Watch your riffles.  If they are not clearing to your desired level, then adjust. Pretty simple right? Seems that way but we start to get into more issues.
Too many people focus on “large rocks” cluttering up their sluice box.  In order to solve this problem they increase the pitch and water. Now the “rocks” are clearing out.  However…. The focus has now been diverted away from proper “GOLD RECOVERY”, to the issue of “ROCKS”. 
Instead you need to REMOVE the rock issue and focus on the gold recovery. This is where CLASSIFICATION is an absolutely a TOP, VERY important, key issue. While it does slow down the amount of material worked in most systems, the extra time is worth it.
 Again, if you are “TUNING” your equipment not to hold ROCKS, then you are NOT tuning it to capture gold in the most effective manner.      
Simply removing the ROCK issue via classification will allow you to FINE TUNE your sluice and capture more gold.










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