Compressor House Approximately 7 Metres West of Pump Engine House to Marriott's Shaft on South Wheal Frances Sett

The compressor house, located approximately 7 metres west of the pump engine house for Marriott's shaft on the South Wheal Frances sett, is a derelict structure from the late 1890s, built for the South Frances United Mine. It is constructed of uncoursed granite rubble with quoins and features brick arches over its openings. The building has a rectangular plan measuring three by two bays and is oriented on a north-south axis. It stands two storeys tall, with round-headed windows on the first floor. The west side includes a square-headed doorway, accessed by four steps near the north end, seven small rectangular openings at ground level (which are tunnels or conduits piercing the foundations), and three large windows on the first floor. The east side mirrors this layout but lacks the doorway. The gable walls have square-headed windows at ground level, round-headed windows above, and small circular windows at the apex. Inside, there is a solid concrete plinth up to the first floor level, featuring a central cut-out and a recess for a fly-wheel. Historically, the compressor house housed a cross-compound two-stage plant by Fraser and Chalmers, which was capable of operating 30 rock drills. This building is part of a significant group of remains from one of the best-equipped mines in Cornwall, which closed in 1918.