The Rio Tinto/old Giroux property embraces 9 patented mining claims on a 166 acres adjacent to the town of Darwin, California. The Rio Tinto, Mammoth, Magnet, Mexican, Republic, Kingston and Toga 1,2 and 3. According to historical documentation from 1890-1908 mining produced Cu-Pb-Zn from a 200 foot shaft with a 9 foot cross cut and 70 foot inclined shaft.
My grandfather, who was a prospector and miner, obtained this property in 1946. He was unable to work it due to other obligations and later declining health. After he passed away my grandmother leased the property to a single man who had a corporation called "Harvest Gold Corp." in 1992. Although he was very positive about the mine, He had to cancel the lease a couple years later due to lack of exploration funds and inability to raise capital. In the short time he leased the property he did do a chemical analysis on samples which showed Paleozoic limestones in a thrust fault contact with the Darwin Diorite stock, skarn mineralization with copper and gold in and near the thrust surface. He thought that a hidden copper/gold target was present but he was unable to pursue the positive findings. The property has not been worked on since.
In 1980 a report written by the University of Western Ontario for potential Tungsten occurrences in the Darwin Hills, in the Giroux/Kingman area wrote that there was an area with a continuous band of garnet skarn 2500 feet long and up to 250 feet thick that contained disseminated copper oxides and sulfides that had been exploited. The overall skarn band was extensive to the depth well beyond the bottom of the Giroux shaft (203 feet). Dumps at the various workings contained jasper/limonite/copper oxide material as well as minor gold and silver. Another of these areas at the old Giroux and Kingman mines had a thick extension of skarn zone with good depth potential disseminated copper mineral and stratigraphic and structural setting comparable to many of the W/Cu deposits in the Yukon. The report said that the area needed careful examination as a Cu and possibly W, Au, and Ag prospect.
Location and Access:
The claims are adjacent to Darwin township in the Darwin Hills which is a NW trending range immediately east of the town of Darwin which is 36 miles southeast of Lone Pine, Ca. and 40 miles west of Death Valley in Inyo County, California. It is reached by taking State Highway 136 east to the intersection of State Highway 190 at the south end of dry Owens Lake, then proceeding on Highway 190 approximately 13 miles to the Olancha Darwin Road turnoff. Turn south on Olancha Darwin Road and travel 5.5 miles to the ghost town of Darwin. The Rio Tinto claims are easy to access from a dirt road on the outskirts of the town
The Darwin District is an area of low arid hills within the Darwin Plateau in west central Inyo County. The Rio Tinto consolidated claims include 9 claims on 166 acres of that district.
In the Darwin Hills a deformed middle to upper Paleozoic shelf sedimentary sequence is intruded by a Jurassic-Cretaceous quartz monzonite stock. The Pennsylvanian-Pernxon Keeler Canyon Formation is the principal unit in the Darwin Hills. It is flanked to the northeast by the Permian Owens Valley Formation and in fault contact to the west with the Pennsylvanian Lee Flat limestone.
There are many individual mines in the Darwin area distributed throughout an area encompassing approximately 9 square miles and called the Darwin District Mines. They have operated intermittently since 1875 and have been the principal Pb producers of California with approximately 29 million dollars in lead, silver, zinc, tungsten and copper. The location of many of the deposits in veins and the composition of the associated skarn and kornfels makes the Darwin W deposits unlike any major deposit described in the literature.
Currently there is activity in the Darwin Hills. There is at least one mine that is actively being worked. The company that is currently working the mine have invested heavily in it for the past 20 years. They have had a record high profitability of 40 percent direct shipment of ore and four to one ore to waste ration. It is a primary producer of Tungsten, Zinc, Silver and Lead. The mine contains over 138 miles of drifts and 3.2 million tons of ore and waste produced.