Challenge deposit, Redwood City, San Mateo Co., California, USA
|Latitude & Longitude (WGS84):||37° 27' 57'' North , 122° 15' 16'' West|
|Latitude & Longitude (decimal):||37.46611,-122.25472|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
A former Hg deposit/mine located in the approximate center sec. 36, T5S, R4W, MDM, 2.7 km (1.7 miles) SW of Redwood City (center), just inside the western boundary of the city. Owned by A.F. Oddstad, Jr. First produced in 1955. MRDS database accuracy for this location is not stated. Now part of a housing development.
Mineralization is hosted in Late Jurassic-Late Cretaceous serpentinite of the Franciscan Formation. The ore body is irregular. Serpentine occurs as float. The ore is in slump rock and alluvium. Local alteration includes the silica carbonate alteration of serpentine. Local rocks include ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains).
Workings included surface openings with an overall width of 15.24 meters. Operations terminated in 1958 so that the area could be developed into a housing area.
Production statistics: Year: 1962 (period = until 1962): estimated ^6 to 10 pounds (3,614 grams) Hg/metric ton.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
17 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 - Jurassic|
66 - 201.3 Ma
|Franciscan Complex, Sheared rock (melange)|
Age: Mesozoic (66 - 201.3 Ma)
Description: Predominantly graywacke, siltstone, and shale, substantial portions of which have been sheared, but includes hard blocks of all other Franciscan rock types. Total thickness of unit is unknown, but is probably at least several tens of meters
Reference: Brabb, E.E., R.W. Graymer, D.L. Jones. Geology of the onshore part of San Mateo County, California. U.S. Geological Survey Open-File Report 98-137. 
|Late Jurassic - Middle Jurassic|
145 - 174.1 Ma
|Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains)|
Age: Jurassic (145 - 174.1 Ma)
Stratigraphic Name: Josephine Peridotite
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.