Western most history sign on pier at Sumpter Valley Dredge
Marker Name: The Inside Scoop
Marker Text: As each bucket came over the top of the digging ladder, its material was dumped into a large hopper. From there, everything fed into a cylindrical screen - 6 feet across by 35 feet long - that continuously tumbled the material. High pressure water - 3000 gallons a minute - rushed over the screen and its contents. Gravity and water forced the material down the length of the screen. The material, including gold, fell out into a catch pan below, while the larger rocks and gravel were carried to the rear of the dredge and dumped into tailing piles by the stacker.
Inside, water continued to wash the finer sands, pebbles and precious minerals from the catch pan through a series of sluice boxes. Just about the whole back of the dredge was covered with sluices. In each one, there’d be a number of “riffles,” kind of like a washboard. The sand and gravel were washed away while the heavier gold was trapped in the riffles.
As years passed, more efficient means of trapping the gold were developed. They added a box like contraption - called a jig - partly filled with round metal balls, like B-Bs. Sand escaping - from the riffles would drop into the jigs - where the balls would pulverize the material. Mercury added to both the riffles and the jigs would attach itself to gold in the fine sands. This method was far more efficient at removing gold.
Very few people had access to the gold, at least officially. Though there are tales of embezzlement, the security of the gold became tighter as the years went by. After separating the gold from the mercury, it was pored into bricks for shipment to the US Treasury.
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