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Temescal Tin Mine (Cajalco Tin Mine; Temescal Mine; Temescal Tin District), El Cerrito, Riverside Co., California, USA

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Latitude & Longitude (WGS84): 33° 50' 53'' North , 117° 28' 51'' West
Latitude & Longitude (decimal): 33.84813, -117.48087

A former Sn occurrence/mine located in the SW¼W½S½ sec. 2 and in secs. 3, 10 & 11, T4S, R6W, SBM, 4.0 km (2.5 miles) ENE of El Cerrito, W of Lake Mathews, along the SE margin of Eagle Valley, in an unincorporated area, on private property. Property consists of 870 acres in the western part of Rancho el Sobranto de San Jacinto (about 5 miles SE of Corona and 11 miles SW of Riverside) Discovered in 1853. First produced in 1869. MRDS database stated accuracy for this location is 100 meters.

Mineralization is hosted in Late Cretaceous quartz monzonite. The ore body strikes N35E and dips 65N at a thickness of 1 meter, width of 1 meter and a length of 40 meters. Ore body No. 1 is pipe-like and disseminated. Ore body No. 2 is irregular and in a fissure vein. Ore body No. 3 is a replacement body. The primary mode of origin was hydrothermal activity. The secondary mode of origin was contact metasomatism. Primary ore control was fracturing and the secondary control was the contact zone. The deposit is comprised of 65 veins. Tin occurs as cassiterite in black tourmaline veins in coarse-grained hornblende-biotite granite. 65 veins are present but only 10 have been explored. They vary from 1 inch to 15 feet in width, averaging 1 to 2 feet. The general trend is N20 to 50E, dipping 50 to 85 NW. The veins contain quartz also. Most veins are less than 1,000 feet long and discontinuous. The main vein, Cajalco, is over 690 feet in depth. Cajalco is exposed over 550 feet in length, strikes N55E and dips 55 to 80NW, at 1 inch to 5 feet, 10 inches thick. Cassiterite occurs as disseminations, bunches and stringers. The country rock is a quartz monzonite (?). Wallrock alteration is intense (sericitic, silicification and propylitic). Local rocks include Mesozoic granitic rocks, unit 2 (Peninsular Ranges).

Workings include surface and underground openings. Only 10 veins have been explored by tunnels and shafts.

Analytical data results: The ore grade averaged 4.0% Sn oxide, or 0.15% Sn.

Mineral List

3 valid minerals.

Rock Types Recorded

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Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

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66 - 145 Ma
Cajalco Pluton: Monzogranite

Age: Cretaceous (66 - 145 Ma)

Description: Most of western part of pluton is medium-grained, equigranular, hypautomorphic-granular to subporphyritic monzogranite and subordinate granodiorite. Includes variable amounts of angular inclusions, mostly, if not entirely derived from stoping of Estelle Mountain volcanics of Herzig (1991). Number, size, and reliability of idenity of inclusion parent rock increases from east to west. In western part of pluton included masses of volcanic rock comprise large volume of pluton. In northern and northeastern part of pluton stoped masses of hornblende gabbro are abundant. Unit includes relatively fine- grained leucogranite, especially in area northwest of Lake Mathews

Reference: Morton, D.M., F.K. Miller . Geologic Map of the San Bernardino and Santa Ana 30' x 60' quadrangles, California. U.S. Geological Survey Open-File Report 2006-1217. [42]

Late Cretaceous - Middle Jurassic
66 - 174.1 Ma
Mesozoic granitic rocks, unit 2 (Peninsular Ranges)

Age: Mesozoic (66 - 174.1 Ma)

Stratigraphic Name: Bonsall Tonalite; Bradley Granodiorite; Cactus Quartz Monzonite; Cajalco Quartz Monzonite; Corona Hornblende Granodiorite Porphyry; Domenigoni Valley Granodiorite; Escondido Creek Leucogranodiorite; Estelle Tonalite; Fargo Canyon Diorite; Green Valley Tonalite; Home Gardens Quartz Monzonite Porphyry; Indian Mountain Leucogranodiorite; Lakeview Mountain Tonalite; Lake Wolford Leucogranodiorite; La Sierra Tonalite; Mount Hole Granodiorite; Rattlesnake Granite; Roblar Leucogranite; San Jacinto Granodiorite; Stonewall Quartz Diorite; Woodson Mountain Granodiorite

Description: Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Comments: Peninsular Ranges. Primarily tonalite, granodiorite, and minor quartz monzonite and granite. Emplacement ages mostly 80 to 105 Ma in eastern part of area and 105 to 140 Ma in western part; minor Jurassic rocks in central part

Lithology: Major:{tonalite}, Minor:{quartz diorite,granodiorite,quartz monzonite}, Incidental:{granite, pegmatite}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Segerstrom, R.J. (1941), Tin in California: California Division Mines Report 37: 531-557.

Palache, C., Berman, H. & Frondel, C. (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged, 834pp.: 579.

Page, Lincoln Ridler and Thayer, T.P. (1945) The Temescal tin district, Riverside County, California. USGS unpublished report, 24 pp. (On open file, California Division of Mines and Geology library, Sacramento).

Sampson, Reid J. & W. Burling Tucker (1945), Mineral resources of Riverside County: California Journal of Mines and Geology, California Division of Mines and Geology (Report 41): 41(3): 153-154.

Bedford, R.H. & F.T. Johnson (1946), Survey of tin in California: US Bureau Mines Report of Investigation 3876: 8-9.

Gray, Clifton Herschel, Jr. (1957), Tin in: Mineral Commodities of California, California Division of Mines, Bulletin 176: 641-646.

California Division of Mines and Geology Open-File Report 77-14 (1977): 973-978.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10077106 & 10212629.

U.S. Bureau of Mines Minerals Availability System/Mineral Industry Location System (MAS/MILS): file #0060650977.

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