Igneous rocks, generally, are the site of ancient volcanos, or at least active undersea cracks. Igneous rocks tend to have the interesting minerals in them. T

Igneous rocks, generally, are the site of ancient volcanos, or at least active undersea cracks. Igneous rocks tend to have the interesting minerals in them. Take the gold deposits of southeast alaska. When they were formed, geologists think, they were probably black smokers near undersea cracks that belched out plumes of gold bearing minerals. Several million years of continental drift and they are strata under mountains