I may be wrong, but I expect that one that holds concentrates may well have no avenue for marketing. The metals markets are structured such that unless you have huge volume, on a repeat basis, you must deal with those that accumulate. I found that to be true when I marketed my many years accumulation of platinum. Not many readers, here, would consider owning in the vicinity of 70 ounces as not being significant. but one of the major refiners (JM, to be exact) had no interest in discussing my offering.
Ores would be even more difficult. Custom smelters are virtually extinct now, although there may be one, somewhere, that might entertain small volumes. I know that the one I used in Sparks, Nevada, is long gone.
I really feel that mining is no longer something that can be accomplished on the level of the pick and shovel operation. Might not be true of a high grade deposit, but I dare say a person that has a respectable deposit of base metal ore would have no avenues to pursue, and setting up to process would likely be economically prohibitive. The best one might hope for is to have a claim good enough it can hold the interest of mega corporations.
I'm certainly open to the comments of others. I may be completely out of touch with reality.
Harold