MI-49 Geology of Colorado Postcard Details This 6″ x 8″ post card shows distribution of rocks of different ages. Geology is superimposed over shaded relief of Colorado topography showing mountains valleys, rivers, and some cities. Up to ten paper copies may be ordered for free, please contact us directly at cgs_pubs@mines.edu for those. Otherwise this is a digital PDF download. MI-49D Citations Colorado Geological Survey. “MI-49 Geology of Colorado Postcard.” Colorado Geological Survey, 2010. https://coloradogeologicalsurvey.org/shop/geology-postcard-colorado.