Lol I remember those mining adventures I do with my friends, I usually end up with two diamonds... But in hexxit it's like 2 stacks every trip. They're more common than iron D:
If you have a miner tree those produce any ore but for me redstone is the most common also if you go to the twilight and in those hydra dens you can find a lot of redstone (Shhh I know I'm late)