Until relatively recently, mineral exploration work was fruitfully focused on shallow ore deposits that could be discovered by looking for known ore-related geological features discernible at the grassroots just between the geologist’s or prospector’s feet. Because of the long human history conducting such grassroots exploration work and the fair consistency of ore-related features, it was possible for geologists and prospectors to develop considerable valid expertise in conducting such exploration work. Today, most ore deposit discoveries are still quite shallow but — because of the passage of time, continued industrialization, and supporting mining activity — nearly all of the new shallow discoveries are smaller in size and lower in ore grade than formerly was the case. Conducting deeper mineral exploration in compensation for the depletion of shallow ore deposits (“that low-hanging fruit”) largely means gradually learning to rely on previously unseen (non-grassroots) ore-related characteristics of the country and host rocks. Under such circumstances, the expertise of present day mineral exploration geologists is not yet fully developed and is therefore at least temporarily less reliable.