It says they're common like iron, but I went strip mining for a while and found 40 diamonds, 18 emeralds, no arcane crystals. I'm looking between 8-15 y. I have found them in the past so I know they exist. But I don't think they're supposed to be this rare according to the wiki? Can anyone help?

Closing this as there was no response.

What version are you on? Just tested and they spawn fine for me.