Prospecting assistance

Hello

I’ve been having a rough time with mining ore, specifically finding copper. I’ve followed a vein to what I believe is it’s highest point at 21% with the prospecting pick and the percentage going down when I go up, down, left, and right. I’ve been digging for hours and gone through two picks. I’ve been using the prospecting pick to search for nodes in multiple different spots near the reading and nothing. I’ll dig down, try on the surface, try deep underground, nothing.

Am I doing something wrong? I feel like going through 2 picks just to get copper is a bit much. Is copper more towards the surface? Farther down when the stones start to change? It’s getting to the point where the fun is starting to turn into frustration. Any help would be appreciated