A gem pegmatite mining area located in secs. 25 & 36, T10S, R1W, SBM.
The iron-bearing spinel, pleonaste, is found in the Mack and Victor veins at Rincon, occurring as small (.25 mm.) crystals associated with small garnet crystals. A few imperfect octahedra have been isolated. In fragmented form, the mineral is perfectly isotropic, and deep green in color. Blue spinel has been reported from Rincon at the Mack mine.
References:Rogers, A.F. (1910), Minerals From The Pegmatite Veins Of Rincon, San Diego Co., California. Columbia University School Of Mines Quarterly Journal Of Applied Science, Vol. 31 pp. 208-218.
Murdoch, Joseph & Robert W. Webb (1938), Notes on some minerals from southern California: American Mineralogist: 23: 353.
Hanley, J. B. (1951), Economic Geology of the Rincon Pegmatites, San Diego County, California. Department of Natural Resources, California Division of Mines, Special Report 7B: 24 pages, illus., maps.
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 676.
Weber, F.H. (1963), Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: 309 p., illus., maps.
Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 70, 105, 177, 182, 195, 219, 238, 381.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 429.
Fisher, J. (2002), Gem and rare-element pegmatites of southern California. Mineralogical Record, Vol. 33: p. 389-390.
106 entries listed. 23 valid minerals.
