The Crystal Mill, or the Old Mill is an 1892 wooden powerhouse located on an outcrop above the Crystal River in Crystal, Colorado, United States. It is accessible from Marble, Colorado via 4×4. Although called a mill, it is more correctly denoted as a compressor station, which used a water turbine to drive an air compressor. The compressed air was then used to power other machinery or tools.
The mill was constructed in 1893 by George C. Eaton and B.S. Phillips, promoters of the Sheep Mountain Tunnel and Mining Company. It was built as a power plant for the Sheep Mountain Tunnel. Originally it had a horizontal waterwheel which generated compressed air for miners in the nearby silver mines. It fell into disuse in 1917 when the Sheep Mountain Mine closed. The mill was placed on the National Register of Historic Places on July 5, 1985.