I have seen evidence of a pattern that the time of day (in game) when prospecting plays a big role in the success or failure of prospecting.
I only took screenshots of the success, however, when it turns to night again I can try to get screen shots of the failures.
The pattern is this: at night prospecting is very unreliable, however, during the day prospecting is very reliable.
I came across this because I was prospecting a new Z-level and got three successful prospecting hits during the day. I couldn't break through the cave wall to further explore the node at the time. Maybe a day later IRL, I got a +10 q pick axe and more str and went to work. I mined into the wall in the direction the cones were pointing and used 2 L of rustroot extract to prospect all over the mined out area. Not a single hit! I was using q30+ extract as well! So, I waited until the sun came up (in game) and prospected, and every time I got a hit.
Is this just coincidence or have others been finding the same to be true?