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Jensen Quarry (Oak Quarry), Jurupa Mts, Jurupa Valley, Riverside Co., California, USA

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Latitude & Longitude (WGS84): 34° 1' 32'' North , 117° 25' 54'' West
Latitude & Longitude (decimal): 34.02556,-117.43167
Köppen climate type:Csa : Hot-summer Mediterranean climate

A former limestone/marble quarry located in the SW¼NW¼SW¼ sec. 5, T2S, R5W, SBM, 4.7 km (2.9 miles) NW of Jurupa and 4 miles W of Riverside. MRDS database stated accuracy for this location is 10 meters.

Local rocks include Mesozoic granitic rocks, unit 2 (Peninsular Ranges).

First worked during World War I for marble for cement manufacture by Riverside Cement Company (the same company that owned the more famous nearby Crestmore deposit). Closed in 1927; reopened by Riverside Cement Company in 1948; closed again in 1955. Snow Rock Corporation leased the northeastern section of the quarry from the early 1960s until 1971 to mine dolomitic marble (too high in Mg for cement) for granulated roofing material. The last period of commercial activity was 1974-1979, when Riverside Cement Company removed the last of the cement-grade marble. Since 1979, the remaining pegmatites, impure marbles and other contact metamorphic rocks have been of interest only to field collectors.

In the late 1990's, the abandoned quarry was purchased by a golf club and remodeled into a spectacular course, with white marble and pegmatite cliffs as backdrop, now the "Landmark Golf Club at Oak Quarry" (renamed Oak Quarry by the golf club; not known as Oak Quarry during its active, extractive years), so field collecting is no longer allowed. But the management are proud of the mineralogical heritage of their site, and the course holes bear fanciful mineral names: Biotite Bluff, Calcite Canyon, Garnet Meadow, Graphite Tower, Gypsum Gully, Limestone Dome, Magnesite Terrace, Marble Ridge, Microlite Ledge, Muscovite Marsh, Opal Outcrop, Pyrite Perch, Quartz Corner, Spinel Slide, Tourmaline Tower, Tremolite Pass, Zircon Tumble. The club house has a glass case displaying Jensen Quarry specimens, donated mainly by local collectors Anne Seminaris Davila and Nick Rose.

Mineral List

81 valid minerals.

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.

Click on geological units on the map for more information. Click here to view full-screen map on

0 - 0.0117 Ma

ID: 2252875
Artificial fill

Age: Anthropocene (0 - 0.0117 Ma)

Description: Sand, gravel, and bedrock from pits, quarries, and excavations related to construction, mining, or quarrying activities; mapped primarily where materials are placed for construction of highways, canals, railway grades, dams, and water catchment basins. Only large features are mapped; not shown in some places where unit obscures detailed surficial or bedrock relations. Differs from disturbed ground (Qdg) in that generally large amounts of rock and (or) sediment have been imported to site

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]

Holocene - Pliocene
0 - 5.333 Ma

ID: 2885167
Quaternary alluvium and marine deposits

Age: Cenozoic (0 - 5.333 Ma)

Stratigraphic Name: Temescal Formation; Modesto Formation; Victor Formation; Alameda Formation; Aromas Red Sands; Bautista Beds; Brawley Formation; Borrego Formation; Burnt Canyon Breccia; Cabezon Fanglomerate; Campus Formation; Casitas Formation; Chemehuevi Formation; Corcoran Clay; Cushenbury Springs Formation; Dos Picachos Gravels; Dripping Springs Formation; Frazier Mountain Formation; Friant Formation; Harold Formation; Heights Fanglomerate; Hookton Formation (part); Huichica Formation; La Habra Formation; Manix Lake Beds; Mohawk Lake Beds; Montezuma Formation; Nadeau Gravel; Ocotillo Conglomerate; Orcutt Formation; Pacoima Formation; Pauba Formation; Peckham Formation; Pinto Formation; Resting Springs Formation; Riverbank Formation; Rohnerville Formation; San Dimas Formation; Shoemaker Gravel; Temecula Arkose; Battery Formation; Bay Point Formation; Colma Formation; Lindavista Formation; Lomita Marl; Merritt Sand; Millerton Formation; Palos Verdes Sand; San Pedro Formation; Sweitzer Formation; Timms Point Silt

Description: Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast.

Lithology: Major:{coarse alluvium}, Minor:{fine alluvium}

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.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Rocks & Minerals (1932): 7: 98.
Rocks & Minerals (1933): 8: 80.
Pabst, Adolf (1938), Minerals of California: California Division Mines Bulletin 113.
Murdoch, Joseph & Joseph J. Fahey (1948), Geikielite, a new find from California (abstract): Geological Society of America Bulletin: 59: 1341-1342.
Murdoch, Joseph & Joseph J. Fahey (1949), Geikielite, a new find from California: American Mineralogist: 34: 835-838.
MacKevett, Edward Malcolm, Jr. (1951), Geology of Jurupa Mountains, San Bernardino and Riverside Counties, California: California Division Mines, Special Report 5, 14 pp.
Anonymous (1955), World news on mineral occurrences: Rocks & Minerals: 30: 141-142.
Cooney, R.L. (1956), The mineralogy of the Jensen and Henshaw quarries near Riverside, California: Unpublished Master’s thesis, University of California at Los Angeles.
Mineralogical Magazine (1964): 118.
Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 68, 115, 137-138, 198, 207, 222, 285, 288, 295, 371.
California Division of Mines and Geology Open-File Report 77-14 (1977): 787-788.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 55, 70, 72, 76, 85, 90, 94, 97-98, 103, 130, 143, 145, 146, 150-151, 170, 173, 200, 211, 221, 226, 236, 287, 316, 319, 336, 348, 362, 367, 368, 380, 387, 392, 398, 406, 420, 428, 431, 434, 444, 458, 461, 475, 479, 483, 486, 490, 498, 502, 507.
Devito, F. and Ordway, A. (1984). The Jensen Quarry, Riverside County, California. Mineralogical Record: 15(5): 273-290.
Lapis (2003): 28(12): 9.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10077139 & 10164451.
U.S. Bureau of Mines Minerals Availability System/Mineral Industry Location System (MAS/MILS): file #0060650535.

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