Muon attenuation in matter can be used to infer the average material density along the path length of muons underground. By mapping the intensity of cosmic ray muons with an underground sensor, a radiographic image of the overburden above the sensor can be derived. Multiple such images can be combined to reconstruct a three-dimensional density model of the subsurface. This article summarizes selected case studies in applying muon tomography to mineral exploration, which we call muon geotomography.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'.