The pro pick makes no sense what so ever, it's a chance indicator of ore in an prospected chunk. So it is a gamble most of the time since there is a chance there is no ore.
We were looking for gold (its in quartz under ground) you can't find it with the pro pick.
We were getting so frustrated trying to find this stuff so I installed a scanner mod.
Halite deposits don't get detected where they are at all.
Quartz and gold never show up on a chunk prospect so finding gold is just luck.
I used a scanner mod and we finally found stuff we were never going to find without it (see the attached image).
We are missing out on loads of stuff in the world since there is no reason to go dig for 3 hours and burn through all your iron/copper or run into a cave with nothing but drifter hoards.
The whole prospecting thing needs a rework to make it more usable and user friendly,
And make it so you can spot the hidden underground ruins with rust spots top soil or sounds or something.