Monday, August 18, 2008

How to Run a Sluice Box

How to Run a Sluice Box (Part 1)

Large amounts of gold-bearing material can be processed by a sluice box that is correctly set up and running at peak efficiency. In this post I'll walk you through the first three steps of operating a sluice box out in the field:

1) Setting Up the Box

Find a promising stretch of stream with sufficient water flow to run your sluice box easily and efficiently.

Minimize the distance from the location of the gold-bearing material you want to process to where you set up your box. (Remember, the farther away your digging site is, the more effort and toil you must expend hauling buckets of gold-bearing material to your box.)

Set the sluice box into the stream flow at lateral and vertical angles that will allow the stream current to move fast enough to carry material through and out the opposite end of the box. (Don't fully submerge the box; typically, a water flow depth of 30%-80% works best, but each set up varies.)

Brace the box with large rocks on the side (if necessary) to prevent it from being swept away by the current or water surges.

Test the strength of the flow through the sluice box by shoveling some gravel into the flared "feeder" trough at the upper end. (If the current washes the lighter materials through fairly quickly, you are in business. However, if material immediately "packs up" and the larger rocks and pieces of gravel remain in place, reposition the box until a stronger flow is established.)

2) Starting Up

Screen your gold-bearing material using a 1/4-1/2 inch "classifier" into a 5-gallon bucket. (This enables you to process material more easily than by direct shoveling unsorted gravels. However, some wet or clayey gravels do not classify very easily and you may have to bypass this step on some occasions.)

"Feed" the gold-bearing material in steady, measured amounts into the upper end of the sluice box. (In most manufactured boxes the upper or "feeder" portion of the box is flared to accommodate greater amounts of gravel more efficiently.)

Reduce both the amount and frequency of your material "feed" if you can't see the tops of the box's riffles. (This is an indicator that the riffles are "packing up" and you may be losing gold.)
 
3) Minding the Store
Check the sluice box on a continuing basis for the following signs:
  • Inadequate water flow typified by larger rocks hanging up in the box or "pack ups" behind the riffles.
  • Material packing to one side indicating that your set up is uneven.
Solve these issues by:
  • Clearing obstructions with a shovel, large "stir" stick, or your fingers.
  • Repositioning the sluice box laterally or vertically, or moving the entire box to an area of better stream flow.
Keep a sharp eye out for visible gold in the upper reaches of the sluice box after multiple runs of material have passed through it and cleared the lower end. If you see little or no gold you must ask yourself these two questions:
"Is the material I'm running barren or does it only contain very fine gold values?" or "Is the box not set up properly?"

Answer those questions and then fix the problem. Why? Because a sluice box with no visible gold in it is NOT a good sign. Trust me on that one.

Shovel away all the tailings accumulating underneath the lower end of the sluice box on a regular basis. (This ensures a steady water flow rate and prevents "packing up" from occurring elsewhere in the box.)
(c)  Jim Rocha (J.R.)  2008

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