Surface dredges float on the surface of the water. The material is propelled or pumped to the top throughout a suction hose into a resourceful sluice box that has the ability to gather particularly fine particles of fine gold. The sluice box can either sit on the bank, or float on the surface of the water. An additional plus of the surface dredge is it can without difficulty be used with or without diving equipment.
One very popular inflatable tubes that are commercially made and good to use are the Marlex floats. These are very popular because they are more stable then other ones and they have been designed precisely for dredging. Inner tubes are also convenient because they can be deflated and packed easily, however they can get holes in them.
One other very good thing about surface dredges is that they are easy to use without having to use diving equipment, which is different in the case of the submersible kind. it is very easy to use one of these on the surface with only waders or boots so that the person working does feel the coldness of the water.
Out of all the different types of surface dredges that can be found today, some of the most popular ones are the Triple and Double Sluices since they have better capacity to get a much better and finer grade of gold and black sand concentrates.
Triple Sluices can be found in the larger style dredges starting at four inches to larger. In most cases, the smaller size dredges (the ones that are three inches or smaller) are usually equipped with double sluices.
Concentrates of black sand are very searched out for these days because in many cases they have particles of micron gold in them. Often times the concentrates can be anywhere from one to twenty dollars a pound. This is even more important in the bigger dredges where much bigger amounts of gravel is processed. In many cases this is not a big issue with the small dredges since they only have a limited capacity of processing gravel.
If you are not sure what a triple or double dredge looks like, well, you do well in asking. There is a difference between one or a double or triple sluice and this consists in that a single sluice box processes all the material through one sluice box alone and does not classify it at all.
The double and triple sluices classify and size out the material before they go inside the recovery area of the sluice box. This is a very important characteristic because many times the high speed that is needed to move the bigger rocks and gravel through the sluice box can take some of the fine gold back into the river. To be able to recover the fine gold in the sluice box it is important to run the smaller gravel as slowly as possible making sure not to cause too much waste material to build up. If it is designed the right way, a sluice box will clean it self and work for many hours without needing constant cleaning.