Big Horn Mine  (Bighorn Mine; Lapis Lazuli deposit), Stoddard Peak, San Gabriel Mts, San Bernardino Co., California, USA
|Latitude & Longitude (WGS84):||34° 12' 36'' North , 117° 38' 48'' West|
|Latitude & Longitude (decimal):||34.21002,-117.64668|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
Summary: A lapis lazuli occurrence/mine located in the SW¼ sec. 31, T2N, R7W, SBM, in the headwaters area of Cascade Canyon, on National Forest wilderness land (Cucamonga Wilderness). Owned & operated by Sam Speerstra (100%), California (1990). MRDS database stated accuracy for this location is 10 meters. The deposit is one of the only known sources for jewelry and carving grade lapis lazuli in California.
NOTE: The USGS MRDS database file refers to MRDS file #10110938 (Big-Horn Mine) as a related file. It has no apparent relationship to this locality.
Geology: Local rocks include pre-Cenozoic metasedimentary and metavolcanic rocks undivided.
Workings & Production: Word of the discovery of gem-quality blue lapis lazuli in Cascade Canyon was first reported to D. B. Sterrett of the United States Geological Survey by mineral dealer R. M. Wilke of Palo Alto in 1910. A small cut along the deposit was developed by local miners who thought the blue color signified the presence of silver, but these workings were later abandoned when assays failed to show any valuable metal in the so-called ore.
On May 12th of 1979, Sam Speerstra located a lode mining claim to the deposit, naming it the Bighorn Mine. During a brief period, the mine yielded lapis of the highest quality from what was determined to be a vast deposit exposed vertically from the top of the ridge to the canyon floor below for a distance of 300 feet along strike. Speerstra employed a crew of three men to produce between 50 and 150 pounds of lapis lazuli rock per day.
Speerstra advertised the lapis lazuli produced from the Bighorn Mine for sale consisting of rough pieces with some matrix ranging in weight from 1/2 ounce to several pounds; for $20.00 per 1/2 pound, $35.00 per pound. The best or top quality material was priced at $30.00 per 1/2 pound, and $55.00 per pound respectively. Commercial mining had reportedly ceased by 1980.
Note: The area is part of the National Forest system, and has been encumbered since 1964 by the Cucamonga Wilderness, designated for the protection and management of desert bighorn sheep, which has prevented further commercial mining in the area due to the withdrawal of mineral entry under the general mining laws of the United States.
4 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
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 Macrostrat.org
|Cretaceous - Paleoproterozoic|
66 - 2500 Ma
|pre-Cenozoic metasedimentary and metavolcanic rocks undivided|
Age: to Cretaceous (66 - 2500 Ma)
Stratigraphic Name: Kings Sequence; McCoy Mountains Formation (part); Palm Canyon Complex; Placerita Formation
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. 
66 - 145 Ma
|Monzogranite and granodiorite|
Age: Cretaceous (66 - 145 Ma)
Description: Medium-grained, sub-porphyritic to equigranular, massive biotite monzogranite to granodiorite, commonly leucocratic. Phenocrysts are potassium feldspar. Weathers pale gray. Occurs mainly as large, northeast striking dikes up to 0.5 km wide, cutting Cretaceous tonalite of San Sevaine Lookout (Kss), west of Lytle Creek. West of Deer Canyon (fig. 1) and south of Icehouse Canyon, orientation and shape of bodies are much more irregular, and some intrude Paleozoic metasedimentary rocks in addition to tonalite of San Sevaine. Smaller isolated bodies occur farther west in San Gabriel River drainage. Based on uranium-lead isotopic data, May and Walker (1989) interpret age of Kmg dike near mouth of San Antonio Canyon to be 78 Ma
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.