If you are prospecting for gold, a dredge is only one of the many pieces of equipment you may use in your quest, though if you do use one, you are probably a more serious prospector than the many weekend warrior types that hunt for gold.
Dredges can be simplistic in design or they can be elaborate and cost several hundred dollars. Most gold dredges are suction dredges and come in a range of sizes.
The smaller suction dredges can be carried in a backpack if you intend on hiking to the area you are prospecting with the smallest being a 2″ suction dredge.
While 6″ or 8″ doesn’t seem very big, they are industrial size dredges that require two men to transport it to the claim or the site where you intend to do gold prospecting.
The size of the dredge, not the engine size or the size of any other components connected to it.
There are much larger dredges as well, which are used by larger corporations to dredge for gold and other minerals.
These are large pieces of machinery with a scoop at one end that scoops up dirt, sand, rocks, etc., from a river bed and dumps it into buckets in front of the dredge and these buckets then dump the material into rotating cyclinders.
The excavated material is then sifted through using water and the heavy rocks are dumped behind the dredge.
The cylinders contain holes in which the lighter, smaller rocks or, hopefully, gold drops through into a sluice box.
Suction dredges are similar to a vacuum in which they suck material through them and dump it into sluice boxes, which in turn helps to sort out the heavier rocks from the sand, gravel or sediment found in the water.
These suction dredges can float atop the water or there are some that are submersible and can suction material out of the water onto the sluice box to be sorted through by both the machine and then the prospector.
A gold dredge can be very expensive, with an 8″ suction dredge costing thousands of dollars.
A prospector would have to be very serious about searching for gold to use one of these dredges and even a weekend prospector would probably spend about $1300 for a small 2″ dredge that can be backpacked onto a site and used in the quest to find gold.