[1] It is unknown how much gold these mines produced but they were worked from at least 1855 and perhaps earlier by Californio and New Mexican miners from Agua Mansa.
[2]: 97 The mines were on the property of the Rancho El Sobrante de San Jacinto which by 1893 had come into the hands of an English syndicate, the San Jacinto Estate Limited of London.
The California Journal of Mines and Geology, Volume 11, 1893 reports these Gavilan Mines: M. C. Westbrook and Associates, leased most of the mining area from the English syndicate in 1891, planning a town site at the mines called Westbrook.
However, when the report writer visited the mines in 1893: Shortly afterward Westbrook and Associates sold the lease to the mines to the Gavilan Mining and Milling Company for a period of ten years.
The Ida Leona mine continued to be worked and was most active in the 1930s and finally closed in 1942, having produced $50,000.