The Rinconada Mine is a historic mercury mine, which consisted of eleven claims near Santa Margarita, California. The mine is at elevations of 1,500 - 2,000 feet above sea level. The mine was alleged to have been discovered during Mexican sovereignty, but federal records state it to be originated in 1872 and operating intermittently for the following 11 years. An inefficient furnace operated at the Site beginning in 1876, and the mine was shut down in 1883. High grade operations were believed to have been conducted in 1897, but only yielded small production. The mine was operated in 1915 and shut down again soon thereafter.
In 1920, Rinconada Mercury Corporation began operating the mine and installed a 4 foot by 50 foot rotary furnace. Shortly after, the operation ceased. The operators changed over the course of the following years, with various entities making improvements to the plant and operations continuing from 1925-1926. The plant was not operated again until 1929, when Mercury Corporation of America added more equipment to the Site and assumed operation. In 1930, a fire destroyed the plant, but it was immediately rebuilt and operations continued until late 1932. Over the next 7 years, the mine operated for very short periods by various entities. During World War II, from 1943-44, the mine was utilized for war effort production. It was reopened in 1951 and continued until 1961, with various lessors conducting operations. It is believed that the last period of mine operation was between 1965-1968.
The mine workings consist of approximately 7,000 feet of adits, levels, sublevels, raises and a glory hole. The mine consists of several tunnels, including the Mexican Tunnel, Mahoney Tunnel, Mike’s Tunnel and the Transportation Tunnel. The Italian and Fault Tunnels also were excavated in the search for ore, but it is unclear whether they yielded much ore for the mine process. Most of the mine is still open and accessible and located on BLM and USFS lands. The agencies are working cooperatively to restrict the public from entering the tunnels and holes.
The primary processing and surrounding area is the main area of concern. Most of this area is on private lands. The processing area now consists of a rotary furnace, retorts, dust collectors, condensing units, settling tanks, and a variety of stacks. Formerly, the area contained a jaw crusher, fan, cast-iron pipe condensers and redwood settling tanks. Metal debris is littered all over the processing area and the adjacent stream (a.k.a. Mine Creek). Condenser dust, partially processed materials and mine tailings are located in and around the processing area and in and around Mine Creek, a tributary to Pozo Creek.
There also are two other areas that have been identified as processing areas. One of these areas is near the Rinconada Trail parking lot. It contains a triple D retort in a collapsed aluminum structure. The other area is down gradient of the main entrance road, near a pond and adjacent to the streambed. It contains the remnants of an old retort, consisting of a heating system and 3 pipes with collection. Adjacent to the area and contained in the construction materials of the retort is partially processed materials, condenser soot and tailings.
The mine is adjacent to a recreation area trail and it is evident that the area is widely used for camping, hiking and other activities.
