Now where am I going with this? I am going to explore the idea that gold minerals are being flused right out of the sluice. Some stay in the cons, but in areas with these minerals present the flush might be astonishing. The other thing that might fall out is the amount of fines that blow by the systems. Of course these things have to be present at a given site before this matters.
Lets consider perfect spheres of gold and a lighter gold mineral. From the list in the OP I pick Aurostibite AuSb2 9.98. Almost half gold on a molecular weight basis. (44.8%). And my gold sphere has to pass a 20 mesh screen so max diameter = 0.841mm. Hardly matters what size we start with, but that is in the ballpark for what everyone is sluicing for, right?
Vol of that sphere is 0.31129 mm^3. If pure gold it should weigh 0.006014 grams. Surface area * would be 2.22 mm^2. SA/mass ratio = 369. (mm^2/grams) We can think of that as susceptibility to hydraulic sorting.
Working backwards that equates to a 1.626 mm dia Aurostibite sphere weighing in at 0.0225 grams, of which 0.01 grams is gold. More gold than in that 20 mesh gold sphere. Almost double.
Consider a set up - no classification - that just catches that 20 mesh sphere and things of similar SA/M Ratio. Particles with higher SA/MR get flushed, everything else gets trapped. Anything smaller and/or of greater SA/MR, bye bye. No surprise, everybody knows this. Everybody operates to some size limitation be it hydraulic or screened. Whatever the smallest size fraction recovered for a given operation the rest is blown by. A secondary/tandem sluice with slower hydraulics (larger unit) would tell you how much. Bigger zook fed 'only' by the outfall of a smaller unit. The speed could be cranked aggressively so the small one is skewed to higher concentration of gold and the second one saves any gold rich blow by. Bring home more cons and more gold to work on later via well controlled classification and separation at your liesure. For any given size you could target the gold bearing mineral densities after free gold removal, and resultant 'special' cons could be subjected to chemistry. You could just run a big ole slow sluice to increase your cons mass by being less discriminatory, but with a dual setup you would know right away and easily what the free gold situation is and have it concentrated compared to a much larger volume of secondary cons in the big slow sluice. I don't suggest targeting mineral bound gold in a small operation, but think it might be worth capturing while you are after free gold.
And ... without the secondary trap all those lighter gold minerals of lower density but larger and holding more gold also flush out depending on size up to the equivalent SA/MR. Testing cons wouldn't tell us anything about the mixed mineral blow by from the sluice.
The solution would be optical mineralogy on the bulk material (almost pre sluicing) to see what should be targeted in addition to free gold, and then appropriate classification and sluice conditions to catch it all. Any geology department would be happy to have a gander at your stuff. I'd say start with a hardly separated sample to remove the stuff lighter than the gold bearing mixed minerals. Then decide if you want to bother.
If the numbers above reflect reality, it is easily possible that in gold bearing mineral areas more gold goes off the end of the sluice than brought home free plus in the cons combined.
*It is a lot more complicated than just surface area, we have cross section to flow, sectional density and a host of other factors but lets keep this simple for now. Today we assume a linear relationship for this analysis. We had to chose some basis to explore
