Ore seeds is a mod that gives you the ability to grow the four main ores in Minecraft: Iron, Gold, Diamond, and Emerald. Each seed can be crafted with a nether star and 8 blocks of the ore itself. The seeds are incredibly expensive but worth it in the long run given that you can essentially produce these ores infinitely now.

Iron, gold and emerald are all growable on netherrack surrounding lava and must be grown in the Nether unless otherwise changed in the config file. And obviously be aware of using lava around flammable items. Diamond is grown on coal blocks surrounding lava but can be grown in the overworld.

This is a great mod for reproducing ores without without needing to mine for them.