Placer Mining in BC

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Sluice Boxes and Highbankers

I am not an expert on mining law - I am just trying to help. Use the information in this website at your own risk. See the Notice at the bottom of this page.
For BC, see the Basic Rules about Sluice Boxes and Highbankers.
The Basic Rules page is in the How it Works in BC part of this website - see the green link, above.

Introduction

A sluice box is used to separate gold from gold-bearing material - clay, sand, gravel, etc.

Water flows through a sluice box and gold-bearing sand, gravel, etc. is fed into the upstream end. Gold is very dense - heavy for it's size. It settles on the bottom of the sluice box in places where the water slows down. There are various designs to make this happen.

A Highbanker is a sluice box on a stand, with a built in "grizzly" (grating) to reject oversize gravel, and a water attachment for the sluice and maybe spraying the grizzly. See the photo at the top of the Processing page.

A grizzly is grating or punch plate or coarse screening at a fairly steep angle. Paydirt is dumped on and spray bars might wash it. Small pieces pass through to the sluice box. Larger pieces slide off.

Center of Processing - Keeping the Gold

Sluice boxes are part of almost all placer mining operations in BC.

You dig paydirt and process it...

Sluice Box Design

A sluice box has a bottom and sides but is open on top and at least one end. Water flows through the sluice and gold-bearing material is fed into the upstream end. Modern sluice boxes are made of steel, aluminum and plastic.

Small sluice boxes used for prospecting and hand-digging operations are generally 10 to 18 inches across and 3 to 5 feet long. A sluice fed by a large wash plant might be more than two feet across and ten to thirty feet long.

The Mat/Screen/Riffles Sluice Box

The standard design for a long time, and still common today, has three layers on the bottom, all removable: Gold is caught on the downstream side of the riffles, like it is caught behind boulders. Actually, behind each riffle, you get an eddy - a horizontal whirlpool - that can flush out lighter material while keeping the gold. The angles of the metal in the expanded-metal-screen also act as tiny riffles that help gold settle into the carpet or Miner's Moss, below.

The Engineered Bottom Sluice Box

There are a variety of sluice boxes that have nothing like carpet or Miner's Moss, no expanded metal screen and no removable riffles. What they have is a shape to the bottom that does the job of conventional riffles, creating places where the water slows down and gold is caught. The sluice box in the top image is an example.

A major advantage of this sort of sluice is that clean up - removing the accumulated concentrates - is very easy. No carpet or moss - just tilt it up into a tub and run a little water through.

Using a Sluice Box

A sluice box will work best if everything over 1/2 or 3/8ths of an inch is removed first with a classifier (like a sieve in a pail) or grizzly (a grating, maybe made from (part of) a refrigerator shelf).

Angle and Water Flow and Feeding

There is an old rule of thumb that says that the angle of a sluice box should be down one inch for every foot. On the other hand, many highbanker sluice boxes are used at a steeper angle.

Getting a sluice box working properly depends on the sluice and on what you are trying to run through it. You have to experiment.

From time to time, especially after making a change, you should catch some of what is coming out the end and pan it out to see if you are losing gold.

The water flow and water speed have to be high enough to clear out almost all the light sand, but catch some black sand behind riffles.

If you can't get the water flow you need because the water gets too deep, increase the angle of the sluice. If you need the water deeper, decrease the angle or increase the water flow.

Changing the angle of a sluice box changes the angle of riffles or the shaped-bottom. This affects how it works.

Increasing the sluice box angle or the flow of water or both, will increase the speed of the water. This gives gold less time go settle.

Increasing water speed increases turbulence, which...

In a "Mat/Screen/Riffles" sluice box, when the angle and water flow are just right, (most) gold will be retained behind the riffles, while most of the regular sand and some of the black sand (and probably some of the fine gold) are flushed out.

Clay and Fine Gold

Breaking up any clay is very important. If little balls of clay can roll down the sluice box, they can pickup and "steal" gold that has already been caught by the sluice box.

Miners have often ignored very fine gold. It can be a mistake for you to do the same thing. Often the bulk of the gold that you can recover from a claim is fine. For more information, see Fine Gold.

Clean Up

"Clean Up" is cleaning the concentrates out of the sluice box - the black sand, some light sand, and maybe some gold.

Clean up is a chore with the mat/screen/rifle sluices. You have to take them apart, probably at least dip the mat in a tub, maybe do more work on it, flush everything and put it back together.

With the engineered-bottom sluice boxes, you just tilt them up and run a little water through. It is a major advantage if you have to clean up often.

How often you have to clean up depends mostly on how much black sand you are getting and catching in your sluice box.

Some people try adjust the sluice so that much of the black sand is washed out. In some areas, this can make a big difference in how often you clean up.

Other people like to get the black sand - if you get the black sand, you get the gold. This might not always be true for very fine gold, but the basic idea is good. It does mean doing clean up more often.


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