Sluice boxes are a handy tool of the placer prospector and lightweight portable versions may be carried into the back country to check for gold. They are necessary where any large amount of dirt and gravel is to be washed and the gold taken from it for sampling purposes when one needs to know the exact gold content of the gravels. They are not difficult to make, and you can easily build your own sluice box. The lightweight versions are made of aluminum. The old time wood versions consist of boxes commonly 12 feet long, though any length may be used, and of whatever size the mine they ore made for requires. They should never be less than 10 inches deep and the same wide, and for each 3 inches added to the width, add 2 to the depth.
A movable rough bottom, called riffles, is always used in them, to give the gold a place to lodge. Riffles may be made of any old thing, round poles, lumber, blocks and cobble atones being in common use, the best the writer ever used being 1 by 3 battens, set on edge lengthwise of the box, one inch apart, wedged fast with small block. Heavy rocks rolling over them soon wear them t at, however, and other styles are used for economy, and sometimes they are thought to be better for other reasons.
For long strings of boxes, where a large amount of dirt and rock is run through, the cheapest style of good riffles, if timber grows near, is the block riffle, made by sawing six-inch blocks from a log and hewing two sides until they are the width of the sluice box, say 18 inches, leaving half round the other way, and setting them in and, forcing gravel around them to wedge them down. One or more boxes, at the head of the spring, should have riffles more open, though, to catch the coarse gold. The main idea to be kept in view in making a set of riffles is to furnish a spot where the gold can drop in and the running water will wash away the sand, without having the power to raise the gold. In all styles of washing, a string of boxes at least 20 to 30 feet long should be used, and strings of them a mile long are used at some large mines, [where they are cleaned up but once a year.
POLE SLUICE.
When no lumber is obtainable for making sluice boxes, an inferior
substitute, which will serve for ground sluicing purposes, may be
constructed as follows:
Make a trench, as for boxes, three and a half feet wide, making the bottom
smooth and even. Lay a floor of sacks or canvas, beginning at the upper end,
and lapping a little. Cover this with small poles of even size, laying them
crosswise. Lay a straight log about 15 inches in diameter on each end of
these tight against the side of the trench, and stake them down so that the
water cannot move them. Hew the inner side so that nothing can catch against
it or under them, and fill the holes behind with tough clay.
BED ROCK DRAIN.
In working very flat ground it is often desirable to drain the water
from the mine, or pit, at the same time using the lower part of the pit for
dump ground. To do this, start a ditch at the lower end, bringing it up on a
grade of one inch or ore to the rod, until bedrock is found, the dirt being
shoveled in and sluiced away, and the boulders laid in the bottom of the
ditch in such a way that the water will run under and between them. A sluice
fork should be used, and all the small rock thrown on top of the boulders,
thus putting a filter over the drain. A sluice fork, which is merely a pitch
fork, with nine to twelve tines an inch apart, should be in every placer
miner's outfit, it being useful in getting rid of the small gravel when
there is not grade or dump room to wash it away.
Hand fed sluice boxes:
The common, and sometimes the only practical way of working low bars and
river and creek diggings, is by shoveling in. For this style take two or
more sluice boxes 10 inches wide, fitted with riffles of slats, or small
poles. If the bottoms of your boxes are made two inches wider at one end
than the other, they will be easier to set up and make tight at the joints,
for this style requires frequent moving. You can then set the small end of
one box in the big end of the one below, making it tight by shoving them
together. Bring enough water through a ditch across the ground to be worked
to fill the boxes half or two-thirds full. Then set the boxes near the lower
end of the ditch, as to take up all the water, and stop the leaks with rags,
moss or sod, giving the boxes a grade of not less than one-third of an inch
to the foot, full inch to the foot is the best, if it leaves dump enough to
carry away the tailings. Shovel in the gravel to be washed, not lower than
the head of the upper box, and let nature do the rest.
Great care should be taken at all times, and especially when shoveling in, that the sand does not become packed on top of the riffles when gold going into the boxes, as the water is likely to carry it out through into the tailings. The tailings at the end of the last box should be tested occasionally, If coarse gold is going through, set the box you are shoveling into nearly level, and give those below more grade to keep the riffles clear, and so that the dirt will be softened before it is carried through.
Continue on to:
Placer Prospecting: Part I
Placer Prospecting: Part II
Placer Prospecting: Part III
Placer Prospecting: Part IV
Placer Prospecting: Part V
Placer Prospecting: Part VI
Return To:
All About Placer Gold
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