From: BLM P-048 "Mining Claims" online version visited today.

Discovery of a Valuable Mineral Deposit

Federal statute does not describe what constitutes a valuable mineral deposit, therefore the government has adopted the “prudent man rule.” This rule determines value based on whether or not a person will consider investing time and money to develop a potentially viable mineral deposit. This rule was first stated by the DOI in 1894, in the adjudication of Castle v. Womble, 19 L.D. 455 (1894), the holding of which states:
“…where minerals have been found and the evidence is of such a character that a person of ordinary prudence would be justified in the further expenditure of his labor and means, with a reasonable prospect of success in developing a valuable mine, the requirements of the statute have been met.”

In my experience "Discovery" does not mean locating a compliant resource in the first pan or soils sample IMO.  At the next level of title concerning mineral locations, Mineral Patents require another test that is meant to validate a claimants discovery, it is called the "Marketability Test".  This is applied when a claimant has developed the unpatented mining claim to the point where they can demonstrate a mining method that exploits the deposit AT A PROFIT and wants to buy the FEE TITLE from the USA.  The point is that the "Marketability Test" IS NOT applied to the original location of a claim, the Prudent Man Rule is the only "RULE" for a "unpatented" mining claim.

Not Investment Advice, DYODD, Read the "chapter and verse"