In this room are mineral specimens predominantly from Colorado. Some of the minerals are "ore" samples such as gold and silver specimens, and mineral compounds of copper, lead zinc and tungsten. Other minerals are "gangue" minerals, which did not have any value as ore, but may be beautiful or interesting specimens. Colorado's most famous mineral rhodochrosite, is a gangue mineral. Specimens from the Sweet Home mine near Alma, Colorado, have sold for as much as $500,000. The three cases in the middle of the room contain specimens from the John H. Marshall collection, which he donated to the museum. "The John Marshall Collection puts Ouray on the map for mineral collectors to visit and see specimens that many of the area mines provided," said OCHS Board Member Robert Stoufer.
Other cases contain minerals from some of the more famous mines of the area, and the wood and glass case on the north wall contains specimens donated by Becky Byrd, a deceased former resident of the Ouray area. Most of the minerals of this area were formed by hydrothermal processes: hydro means water, and thermal means temperature, in this case hot. The hot fluids which formed many of these minerals were a direct result of volcanic and igneous activity in the area.