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Gold Hog - Classifying Material

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Classification of Material

We could end up writing a whole book on this subject based on all the conditions, equipment and settings each operator has. We will offer some advice and maybe open up some “different thoughts” for you to chew on.

Before you begin.... keep this image in your mind.
These are "pickers" that would NOT go through a 1/8" screen.
HUGE???? Not really. The metal thing on the right is a ball point pen.

Why classify?
For most people, and the common rule, they classify to reduce large rocks from building up in their sluice.  Classifying also allows you to reduce the water flow and pitch of your sluice bed. Smaller / lighter material requires less “force” to push it down and out.  Pretty simple right?

Most miners have riffles in their sluice. Larger rocks can easily stop in front of, behind, or in-between these riffles.  When this happens, the ARMP action of the sluice is reduced to ZERO in that area. Vortexes collapse, matting is covered, and no flow is occurring. Not a good thing at all.

So, if we can classify down to very small material we can reduce the water flow and the pitch and offer a better “sluice environment” for catching gold, especially fine gold.  Making more sense?

Now let’s explore a few thoughts…

The dream nugget theory…
Here is a simple “thought process” that might help many.  Most dream about a BIG nugget in their sluice. For the average miner it rarely, if ever occurs; especially those working areas for placer gold. (Fine)  So I want you to imagine your “realistic dream nugget” for the area you are working. For many a ” nugget is really big.  Seriously… give this some thought and pick your number…  Now I want you to add 1/8” to that number. (Let’s be safe and save you some sleep.)  So, if your “once in a lifetime nugget” is 1/4”, you will add 1/8” and screen to 3/8”. Get it?  You picked the number, now we added 1/8”, just to be safe. 
So screening, classifying or setting your grizzly / classification bars to this level will actually produce more gold recovery.  You can reduce your water flow and pitch and have a better chance of catching all sizes of gold.

Washing large rocks…
Most miners know that large rocks have “material” stuck to them. Sometimes this material may also contain gold.  So, if at all possible we want an “integrated” classification system on our equipment that will both classify material down while also washing larger rocks prior to them being ejected. Not an easy task for some equipment.  However, if done properly this one step can greatly increase recover rates.
Remember, we DO NOT want these large rocks rolling down our sluice bed.
Even the largest mining operations in operation today know that this is critical. Huge equipment, moving tons and tons of material down massive sluices and guess what?  All the material is classified down to ”.    

Removing the “riffles”…
What? Remove the riffles?
Don’t flip out just yet, read on.
Since riffles often cause may “hang up” issues it only makes sense to look at removing them. If you can’t classify material, or don’t want to decrease material run from classifying (often manual feeding) then it makes sense to remove the obstacles that are causing the losses / blockages.  Also, this gives material run a different area in the sluice with more settling action.
This is one recommendation we often give to commercial operations.  We suggest that they convert at least a “portion” of their sluice bed into a riffle-less design.  We want an EASY FLOW / EASY ROLL section that has very little restrictions, obstacles, or barriers that might slow down or hold large rocks.  It also offers a VERY SMOOTH water flow section with almost no turbulence or material “throw up”.  Remember the golden rule… GOLD FALLS FAST. (1mm sphere drops approximately 48” per second through water.)
As an example, we often remove 1/3 of their riffled sluice bed and install small ” expanded metal over our Gold Hog UR mat.  This creates a section that allows ALL rocks to gently tumble down, yet provides an extremely active fluid bed like bottom where gold simply CAN’T escape.  We often like to see this section up high in the sluice bed, and once installed the operators are generally amazed that super fine gold is now being caught and held in the upper portions of their sluice even on long runs.  
This takes a little “mental visualization” on your behalf.  Picture it if you can, a sluice bed that is 24” wide and 20 feet long.  The entire sluice is set up with riffles all the way down.  Some call this the definition of insanity, “Repeating the same action over and over expecting different results”.  Why would you do this?  Our studies have shown you are much better off exposing the SAME material to DIFFERENT “capture environments” during its run down your sluice. (If you have the room.)  Maybe it’s flat gold… maybe it’s wire gold… maybe it’s super fine gold…maybe it’s a round nugget that like to roll… who knows?  Maybe you are creating too much turbulence all the way down and not allowing for “quiet zones”?  But for some reason it keeps “traveling” and not settling or being captured.  
Not only can this help commercial operations, but all prospectors as well. Look at your equipment and visualize it. This often is great improvement to a simple “stream sluice”.  Since water flow is often gentle / limited, having the entire sluice lined with nothing but ” expanded and UR matting allows material to move freely and still offer tremendous capture ability.    

Classification is an important part of good recovery, however we think that understanding WHY you classify is even more important.  Experiment with your equipment, do tests, and as always adjust to what works best for you.









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