Some ores are soft and easily dug (surprisingly, that includes some ores of iron). Some ores are in hard rock that's heavy, hard work to mine even with modern power tools and explosives.
Desirable ores might include cinnabar (mercury ore), gold sand (weathered quartz-based rock with veins of gold, usually mixed with silver and copper), iron sand (one of the original sources of steel), bog iron (naturally occurring source of wrought iron) -- all of which can be dug in quantities sufficient to make it worth a single miner's time with primitive tools.
How easy are these to find? All were known to the ancients, and in ancient and Neolithic times hadn't yet been heavily mined except near the largest concentrations of population -- so if Joe Layman's farm is pretty far out in the sticks, there might well be outcrops of these minerals where he could spot them.
Now, whether Joe Layman would have the knowledge that this particular sort of black sand can be melted into iron with a clay cupola and a very large quantity or charcoal, or that this other one can be heated in a clay pot over an ordinary fire and yield quicksilver is the other question -- and the answer is probably a resounding NO! Before the modern age, few people had any knowledge beyond what it took to make their own living, and the few who did were typically what passed for wealthy (because only the wealthy would have the leisure time to spend learning things they didn't need to know today to put a roof over their heads or food in the stew pot.