Standard mineral accounting depends on having a reliable sample.  Try applying Gy's sample rule, but if it is like most placer deposits the "nugget effect" may make any sample meaningless.  If it is a shallow deposit you may be able to dig sample trenches across the deposit in both directions, but if the deposit is of unknown depth then the only "representative" sample may be the whole sample, (i.e. you won't know what is in the deposit until you have treated it all, and you'll have no idea what you lost).  Not dissimilar to the Klondike Gold Seekers or the "49"ers, which is why most placer mines turn into ecological disasters costing more to close-out properly than any revenue generated.

OK, perhaps a bit more information is in order.  We have good gold assays and grades info and know the recoveries etc for that metal.  The interest here is in the heavy minerals and REEs contained.  There are no nuggets in the sands, by the way.  This is not a Yukon or Klondike style placer and contains almost no gravel, just a compliment of small pebbles, but mainly coarse to very coarse-grained sand.  What I need to know is assuming I have the information required for the formulas, are the same formulas used for mineral sands accounting as would be used for lode deposits (as per the metallurgical accounting formulas in the blog on this website) and if these same formulas are used (for computing recovery factor, concentration factor, mass recovery etc) are there any special considerations or are the formulas applicable at all?  No problems sampling and Pierre Gy's rule is questionable in general IMHO.