Mineral nodes tend to be found on hills and mountains, lakes and rivers, or in mines and caves. It is like this in real life as well. Tectonic activity in the earth's crust crumples the earth's crust and forms hills and mountains. Because of the rich magma that creates them, these areas tend to be rich in valuable minerals. Also caves bring us deeper below the earth's crust, where we are closer to the richest deposits of metals. Lakes and rivers tend to wash up minerals, so they become more concentrated around water. And of course mines and quarries are build because people found them to be rich in valuable minerals. So when you're on your adventures, be sure to hug the hills and explore the caves of the world for the best minerals.