I did some testing if it's helpful. Ores that without fortune return more than one like lapiz and redstone seem to still have increased yield when you use fortune. Ores that only return one without fortune (Diamond, Coal, Quartz, and Emerald) only return one for one for all levels of fortune (not just fortune III). Seems unrelated to tool material.
shay wilson
I did some testing if it's helpful. Ores that without fortune return more than one like lapiz and redstone seem to still have increased yield when you use fortune. Ores that only return one without fortune (Diamond, Coal, Quartz, and Emerald) only return one for one for all levels of fortune (not just fortune III). Seems unrelated to tool material.