Forum

   What exactly is a sluice?  The principle behind a sluice box is to similate the same deposition action that a river performs at flood stage, on a much smaller scale of course.

  Basic construction is of metal, wood or plastic cut or formed to create a trough to channel water and gold bearing material over a set of obstructions called riffles.   These riffles can and have been made from metal, plastic, wood, stones or just about anything the imagination will allow.   It is best to have riffles that are removable for ease of cleaning out the sluice.  You are creating a miniature version of a river channel with obsticals (riffles) providing low pressure zones behind them, much like boulders, trees and other objects in a real river basin will do.

   The idea is for the user to establish a good flow of water down the trough.  The material should be slowly fed into the upstream portion.  Do not dump material into the box!  It is best not to over feed the sluice too quickly as this will overload the riffles.  If material is put into the head of the box too fast, the sand, dirt and rock will not properly wash through the sluice, slowing down the waters flow and clogging the riffles.  When this happens, gold bearing dirt will merely wash over the riffles and out the end of the sluice.   A good tip is to classify (screen out) your dirt prior to putting it into the sluice.  This helps with not allowing too many large rocks from clogging up the correct riffle action.  Rocks in the riffles can actually blow out material from around them, sending potential gold further down the box and maybe out the end of the sluice, returning it back to the stream instead of into your pocket.

  Many of the commercial sluices available on the market have some sort of cloth, carpeting, screening or mat lining the bottom of the box to better aid in the retention of fine gold particles.  Over this is layed the riffles to create the low pressure areas and a place for heavier particles to lodge behind.  Quite a few sluice boxes will have a built in portion at the head of the box wider at the opening and tapering down to the width of the main box to gather in a higher volume of water.  As the water goes into the head, it constricts due to the narrowing of the head, increasing the velocity of the water.  This really comes in handy when the flow of a stream is not sufficiant enough to keep the paydirt that is fed into the sluice in a slurry state and running through the box properly.

  When material is entered into the sluice box head, it quickly stratifies, allowing the heavier materials to work down and crawl along the floor of the box.  As these heavy sands and gold run along the bottom, they will encounter the riffles,  going over them and getting sucked into and held against the downstream side of the riffle due to the lower pressure behind the obstruction.   Another type allows material to fall down into a crevice-like gold trap riffle known as a "drop riffle" type of sluice.  These perform in a similar way to natural crevices in the rocks, holding the gold and black sands within the depression which is sheltered from the higher velocity water pressure from above.

   Stream sluices are a great tool in gold recovery production.  They require relatively little maintainance and if set up proerly, can be worked all day before cleaning.  It is a given standard to have a one inch drop  for every foot of box as a proper slope for the sluice to run.  However, it really depends on the volume of the water and its velocity to find the proper slope.  This may take a bit of experimentation to determine this.  You want the water to carry the paydirt material through the box, depositing the heavy sands and gold behind the riffle obstructions, without over burdening them.  But, you don't want the water to be too fast that it pulls everything out from behind the riffles thus, not allowing any deposition.