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Riffles
There are some riffles that are so simple that they merely consist of nailing a typical lath on the bottom of a board while there are other ones that have welding angle iron to steel plates. All the different types of riffles have their own advantages and sometimes more than one kind can be used or needs to be used in the same sluice.
Riffles are built out of almost any kind of material you can think of with the most common type of wood. Keep in mind that with a lot of use, wood can be very rapidly ground up due to the big amounts of sand and gravel that pass over it. If you are looking for your sluice to last you a good amount of time, we suggest you consider getting the steel, aluminium or any other kind of metal type because it will work well and keep together for a good number of years.
The main idea of the riffle is to set up an obstacle for the sand or gravel that is getting worked on. When it gets to this point of the obstacle, the water forms an eddy and allows the gold to settle close to the riffle. Any kind of obstacles to a stream of water will do the same to some extent. There are certain types of shapes that are much more effective when it comes to creating eddies and as the fineness of the gold gets better, the more complex types of riffles needs to be used so that the gold is able to settle in.
There is not any way it can be preset how many riffles are going to be required or how far apart they should be from one another. This is decided on depending on the composition of the gravel as well as the richness of the gravel and the fineness of the gold you are working with. This is obviously somewhat of a problem for the amateur prospector due to the fact that a lot of people build their own sluice at home and then transport them to the field. If you are not aware of the type of nature of the gravel or the type of placer you are going to be working on, you will need to make a guess in advance as far as to how your riffles will need to be positioned.
There are a good number of sluices that are from eight to twelve inches wide and the sides are from four to six inches in height. The riffles on these sluices can be anywhere from eight to twelve inches apart. Almost all weekend prospectors are going to have to transport their sluices in the trunk of the car or on the top meaning that in most cases the sluices are short and are normally around four to six feet. Another option is to build two sluices and they can then be used in conjunction so as to provide more length.
It is most likely a good idea to test the sluice out in a place close to your home and watch well the way that it works on sands before you decide to take it out on the field. You will need to watch the riffles carefully so as to make sure they do not pack on hard with black sand and so they do not get clogged. If this were to occur the gold would wash right over the riffle. If the water is too violent a lot of the gold will wash over the top as well along with the material that is lighter so be careful.
