Some, experienced in reading and interpreting financial agreements and SEC filings, already know. Those without that experience, should seek professional advice.
Gold needs to be assayed? Not really that important - it should be somewhere around 0.900 to .950 fine. The real questions are - how much total gold did they recover, and how many yards of gravel did they process to get it? By doing this simple thing, they can figure out whether this is a profitable venture or not.
And after a month of "full production", they should have a pretty good idea of the answer.