J. M. MacDonough Ranch Mine, Portola Valley, San Mateo County, California, USAi
| Regional Level Types | |
|---|---|
| J. M. MacDonough Ranch Mine | Mine |
| Portola Valley | Valley |
| San Mateo County | County |
| California | State |
| USA | Country |
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Latitude & Longitude (WGS84):
37° 23' 34'' North , 122° 14' 4'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Portola Valley | 4,594 (2017) | 1.0km |
| Ladera | 1,426 (2011) | 3.3km |
| Woodside | 5,561 (2017) | 4.5km |
| West Menlo Park | 3,659 (2011) | 5.3km |
| Stanford | 13,809 (2011) | 7.0km |
Nearest Clubs:
Local clubs are the best way to get access to collecting localities
Local clubs are the best way to get access to collecting localities
| Club | Location | Distance |
|---|---|---|
| Sequoia Gem and Mineral Society | Redwood City, California | 10km |
| Peninsula Gem & Geology Society, Inc. | Los Altos, California | 11km |
| Santa Clara Valley Gem & Mineral Society | San Jose, California | 31km |
| Mineral & Gem Society of Castro Valley | Hayward, California | 34km |
| San Francisco Gem and Mineral Society, Inc. | San Francisco, California | 45km |
Mindat Locality ID:
92068
Long-form identifier:
mindat:1:2:92068:2
GUID (UUID V4):
a5e0daef-edec-4ae8-8d24-c13aeb265a2f
A former Au-Ag-Pb occurrence/mine located in sec. 30, T6S, R3W, MDM, 1.0 km (0.6 mile; 3,100 feet) N of Portola Valley (town) (½ mile SSE of Searsville Lake), on private land. MRDS database stated accuracy for this location is 1,000 meters. This deposit was worked occasionally from the early 1870's to around 1915. Investigations around 1955 proved it to be of no commercial value.
Mineralization is hosted in Late Jurassic serpentinite and sandstone. The ore body is 0.76 meter thick. The vein is 30 inches thick. Outcrops on the Stanford Estate to the S occur in a brecciated zone of the San Andreas Fault zone consisting of serpentine. The wall rocks are jasper and sandstone. Local alteration includes oxidation. Local rocks include Plio-Pleistocene and Pliocene loosely consolidated deposits.
Workings include surface openings comprised of pits and trenches.
Analytical data results: Samples assayed 0.03 ounce Au/ton, 1.10 ounce Ag/ton and 0.8% Pb.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsCommodity List
This is a list of exploitable or exploited mineral commodities recorded at this locality.Mineral List
1 valid mineral.
Rock Types Recorded
Note: data is currently VERY limited. Please bear with us while we work towards adding this information!
Select Rock List Type
Alphabetical List Tree DiagramDetailed Mineral List:
| ⓘ 'Jasper' |
| ⓘ Quartz Formula: SiO2 |
| ⓘ 'Serpentine Subgroup' Formula: D3[Si2O5](OH)4 |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| Unclassified | |||
| ⓘ | 'Jasper' | - | |
| ⓘ | 'Serpentine Subgroup' | - | D3[Si2O5](OH)4 |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| O | Oxygen | |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| Si | Silicon | |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
Other Databases
| Link to USGS MRDS: | 10103217 |
|---|
Other Regions, Features and Areas containing this locality
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References
