Stones can be found from littering and breaking cracked sandstone, while iron ore can be obtained through recycling, littering, and dream islands. In my personal experience, I find myself getting stones from Pokemon that litter them. I use Bastiodon and Blissey myself, but the following Pokemon can litter them.
- Bastiodon
- Blissey
- Ramparados
- Tyrantrum
- Aurorus
As for iron ore, I usually like to go to the volcanic dream island, which can give iron ore and is accessed via the Arcanine Doll. You can also recycle nonburnable garbage, as one of those gives you two iron ore. It is littered by the following Pokemon.
- Grimer
- Muk
- Garbodor
Iron ore can be littered by Glimmet and Glimmora if recycling is too slow. Stones can also be obtained by using rock smash on cracked sandstone, but that's relatively inefficient.
Source for littering: Serebii. Everything else is personal experience.
