Regarding your second question about geological features, the features may be mapped if they are big enough. This is probably true for granitic gneisses, may be true for pegmatites and conglomerates and unlikely for veins and placers. This will not help you though. Even though the mineral appears in let's say gneisses, 99.9% of gneisses will not contain this mineral. Of those 0.1% that do contain it, only a fraction will have it big enough so you will be able to see with without a microscope, or any larger than a speck of sand.
Finding rare minerals is indeed hard. If however you do indeed come across brannerite, I would like to remind you that it contains quite a lot of radioactive elements so don't make jewelry or good luck charms out of it, and washing your hands after dealing with it is usually a good idea.
Good luck!