Salem

I found an used mine. It was mined for like an area of 20x10 and I started to mine 3 tunnels 1x20 with a gap of 2 tiles to raise my chance to find irons...but I didnt find any. Is it normal that the rate to find iron boulders is so low? I feel depressed

Iron spawns in nodes, not by separate boulders. Where those nodes will be is defined at the moment insides of your map were initially generated. Your tunnels are too close, this way you are actually decreasing your chance at finding anything. Try bigger gaps, 10 tiles or so.
Overall you spent very little time working on your mine so far, 20x10 + 3x20 is not that much and one can't say you are being unlucky just yet.

Ok thank you, how much big are these nodes? like 2x2 or bigger?

They spawn in 'veins' of varying sizes. I'd say they end up being around 5x10. Not solid but at the widest points. Personally I do 4 tiles between my shafts when looking for silver or copper. And 8 for iron.

GreenFox91 wrote:Ok thank you, how much big are these nodes? like 2x2 or bigger?

Size is random, but common metals are typically bigger, here's a copper node for example: