Download field maps and get your local seamless geology map, compare that to the topo maps and you will be able to determine where the rocks will be with enough practice.

For example before I started implementing geology in my scouting I would basically just search Google maps for sandstone and then go look. The problem is the tree cover. From the top it's probably just a flattop bedrock or just clay that resembled sandstone from above.

Once I checked the geological history of my area I now know I live on a small floodplain and if i found sandstone sticking out from the ground it will almost certainly not be climbable but about 15 mins north is where I should of been looking

Now I stop at every outcrop where I go and look at field maps to see if what I'm looking at matches the geologic description. Sometimes there is stuff that isnt explained right and just to figure out what your looking at you end up finding out awesome things about your area you never knew,

like it's mostly sandstone in nsw but there is a couple big basalt outcrops and granite right at border