I'd be happy to clarify..
Almost this entire planet has "trace" amounts of Au, your back yard if you have one, for example.
One does "feasibility" studies based on many in the ground sampling, be it trenching, drilling, surface sampling to determine "if" the ground holds Ore with an amount of Au that can be extracted from the Ore at a profit. The sampling is conducted by one of MANY Geologists, those samples are called ASSAYS. After ALL costs are subtracted from the amount of Au processed, is their revenue remaining? = PROFIT!
Lastly, let's not over look the importance of CHAIN OF CUSTODY while handling sampling and assays!
to catch a fish is not all of fishing. Zane Grey Tales of Swordfish and Tuna 1926
