Classification of Material

It takes more speed of water to move larger material than it takes to move the smaller pieces through the sluice box. Although it depends on the degree the flux of water increases when going through the sluice box, and it will probably depend on how much gold is lost during recovering activity. Said in another way while there is a kind of slow flux of water that runs through the sluice box, there will be potentially more probabilities of recovering fine gold, always that the water power is enough to keep riffles concentrated.

When the biggest rocks are dragged by water through the slice box, they also bring more turbulence in back of the riffles when going over them, which could make us lose some of the fine gold. Because of that to improve gold recovery, it is common practice to first pass through the material through a screen to discard the largest rocks before making the material go through the sluice box. This way we will need less water power to make it pass through the box, which will allow the flux to be better directed when passing over the shorter riffles and thus increase the recovering potential of fine gold.

The action of screening materials is called “classification.” Materials that have already been passed through the classification screen called “classification materials.”

Half an inch mesh screens are commonly used in small and medium scaled sluicing operations because the screen big enough as to quickly classify, leaving out the sluice to materials larger than half an inch. The result of this is that it will be needed less powering the flux of water to go through the box and fine gold recovery will considerably increase.

Classification for sluicing operations can be done in endless ways. One of them is placing a strong piece of half an inch mesh screen on top of the tray or bucket and shovel or pour through the screen into the container while putting them aside and next to the larger material. Once the bucket is full with classified material one can pour inside the sluice box uniformly. Do not pour the contents of the bucket all at the same time. Much of the material could overcharge riffles and cause a greater loss when recovering gold.

In a situation in which it is necessary to carry material on short distances to the sluice box, sometimes it is better to classify material directly into a cart and take in it only classified material to the recovering system. Another good screening method is to build a classification device in which one can shovel directly into it, and which will be put directly on top of the box pouring the classified material into the sluice box.

One can also place a water spray bar to help classify the material and move it downwards and feed the sluice, all at the same time. The device must be built with the screen fixed in an angle. This way, the largest materials will be able to roll out of the screen while the pay-dirt is shoveled in. The smaller materials must fall through the screen and go directly to the head of the sluice box.

Actually, this device is a miniature model of the big classifiers used in large scale bench mining operations. A classification device like this is rather easy and cheap to build and will help you increase the speed of the production and sluicing operation. To screen before will considerably improve the recovery of gold process.