Dunno where ohiochris gets his info but the opposite of what he said is the truth. The drop riffles are definitely better at catching the super fine gold. Even the very first time I ran mine I did better than my buddy with his trusty A52. I have seen it multiple times and even put my angus mackirk at the end of an a52 and caught the fines that sluice missed!!
Im glad you are having such good luck with your drop riffle sluice. Where I got my information was spending almost a year reading everything I could find on the subject which included real firsthand reviews from actual people and not companies , research on how and why riffles/sluices work , plus I talked with quite a few people who used both types. Drop riffles are not so efficient at gradually slowing the water flow and "exchange" is naturally limited in this type of sluice. Anyone can claim one did "better" than another type of sluice , especially when we dont know that each sluice was set up properly for conditions. All Im saying is the physics behind why and how they work do not back up drop riffles as being better for fine gold. Thats all I have where I am at , ultra fine and super thin specks , and few of them , yet my sluice is very efficient at catching them. Maybe what I am saying is just an opinion , but its an educated one , do a google marathon , scour MANY gold prospecting sites and forums , you will see what I have seen. Too often the reports say that drop riffle type sluices work great but are not good for micro gold , too often for me anyway. Maybe your idea of small gold is different than mine , I am talking about gold so small its literally hard to see , almost dust , and Im sorry but that stuff can flow right through a drop riffle sluice without touching a thing unless in a low/slow water situation. All sluices miss some of the fine gold , put another sluice of any type at the end of another and you will find gold that the other missed , and pretty much all sluices will catch some ....but some are better at it than others. I just suggest that anyone looking to buy a sluice do some in detail research first. The information is out there and it backs what I am saying. But MORE importantly , different conditions exist that effect how a sluice works. Drop riffles work best in slower water , in SOME conditions probably better than a raised riffle sluice , I will concede that. Higher volume and fast water though , you really need raised riffles , sticking up into the flow , to slow the water and create eddies that will literally pull the tiny heavies in behind the riffles or they will flow right through. They also make the exchange work more efficiently , working the heavies in and the other stuff out. There are in fact , too many variables to consider in this discussion. Water flow and speed , classify or not , and how much classification , the location and type of overburden , chunky fines or flake. All this probably explains why some have better performance than others with a drop riffle setup. If you dont believe what I am saying thats fine , everybody has their own opinion.
