The Grizzle and Sluice Box

If several rocks are near in the placer material a grizzle will be needed. A grizzle is a row of heavy steel bars which screen out the very coarse rocks .Old mine rails turned upside down and joined to a heavy frame at each end makes a good grizzle. The better material falls through the spaces among the bars and into a hopper lower.  The rocks which do not pass through the grizzle are shoved off to the side. The spacing of the bars will depend on the size of the screen which is used ahead of the sluice. This space is frequently 3 to 4 inches.

The material in the hopper is fed directly into the screen or carried by a conveyer to the screen. The release rate of the hopper or the quantity of material passed by the conveyer belt is controlled to give the correct quantity of feed to the sluice box. A trommel screen is used to screen the material to the size which will be put over the sluice. A trommel is an extended turning cylinder composed of one or more special sized screens. The intake end of the screen is higher than the ejection end so that material will move through the trommel.

Material is fed into the intake end of the trommel and screened by the first screen. The size of the first screen is determined by the size of the material to be put over the sluice. Material screened by the fine screen goes straight onto the sluice box. If very crude gold is present in the placer, the trommel will have a second screen which will size material to be hand picked for large nuggets. The coarse material exceeds through the trommel and is dumped out of the discharge end. The size of the screen or screens used will be definite during the sampling program. The sluice box is the most important piece of gear, since only here can the gold is saved. The sluice should be assemble at least 1 quarter inch thick steel so that the base is flat and smooth. Enough base is no buckling or rippling of the floor.

The slice should be balanced so that the pitch of the box can be altered. Water coming onto the sluice should be controlled so that more or less water can be used at any time.

The riffling and tie downs which hold the carpet in the bottom of the box should be constructed so a smallest quantity of time is required to clean the box. The size of the sluice will depend on how many tons per hour will be fed into the sluice. Still even for a very small placer, the box should be at least 2 feet wide. Timber spacers can be disappearing to the sides of the sluice box to make it narrower if required. The side of the box should be about 10 inches high.