Iridium ore: post 1.6 upgrade, it became rarer to come by. It's best source, is to rush completing community/joja and grab the statue from grandpa's shrine, at year 3.
Radioactive ore: start Mr.Qi's special quests, post collecting all golden walnuts. Finish the Danger in the Deep and Skull Cavern Invasion ones, remembering to activate each place's respective altat, next day come. For farming it, i use luck bufs on very lucky day and use the elevator, for DANGEROUS mines, near the bottom (nodes don't spawn at multiples of 5 floors, i think).
Blacksmith profession helps (the level 5 prerequisite actually, which yields more ores per mine attempt).