El Portal Mine (El Portal Barite Mine; Barium 1 claim; Barium 2 claim; North Barium claim; South Barium claim), El Portal, Mariposa County, California, USAi
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Latitude & Longitude (WGS84):
37° 40' 16'' North , 119° 48' 10'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| El Portal | 474 (2011) | 1.7km |
| Midpines | 1,204 (2011) | 17.5km |
| Wawona | 169 (2011) | 19.7km |
| Yosemite Valley | 1,035 (2011) | 21.2km |
| Bootjack | 960 (2011) | 24.1km |
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 |
|---|---|---|
| Mariposa Gem & Mineral Club | Mariposa, California | 25km |
A former Ba mine located in secs. 18 & 19, T3S, R20E, MDM, 1.8 km (5,900 feet) WSW of El Portal, along the Merced River at Racheria Flat, between river miles 110 & 111 (astride highway 140 and the Merced River). Operated by the El Portal Mining Co. MRDS database stated accuracy for this location is 500 meters. This deposit has yielded about 75% of the baryte mined in California and most of the witherite mined in the United States. The deposit has been idle since 1948.
Mineralization is a Ba/baryte deposit with a lenticular ore body. The baryte and witherite replace limestone associated with the slate, phyllite, and schist of the Calaveras formation of late Paleozoic age. The ore occurs in two distinct belts about 1,200 feet (360 meters) apart. Each belt strikes north and dips east. The lenses of ore, as much as 20 feet thick and 100 by 200 feet long, have sharp contacts with the enclosing isoclinally folded limestone and metasedimentary rocks. The ore is 85% barite and 2 to 3% witherite. Much of the ore is banded and retains the structure of the original rocks.
Within the baryte zone of the North Mine the rock is principally a light gray to white, granular, crystalline rock, in most places about 85-90% barite. Ore in the South Mine commonly contains 85% barite but considerable barite rock falls below that percentage and has not been considered good enough to process. A new barite ore body was discovered during diamond drilling operationsm during the winter of 1949-1950.
The deposit is cut by the west-flowing Merced River; both parts of the deposit have been mined. The deposit is truncated on the north by a small boss of granodiorite. The limestone adjacent to the granodiorite has been altered to calc-silicate rocks by contact metamorphism. Local rocks include Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada).
Workings include underground openings comprised of adits, crosscut adits and stopes. Development work included driving of a crosscut and raise on the lens-shaped ore body.
Discovered and first worked in the 1880's. The first production was recorded in 1910 and operations continued intermittently until 1914-1915. The mine operated more or less continuously from 1929 or 1930 until 1948. It has been idle since 1948. Most of the production was between 1910 and 1948, within which period 398,613 tons of barite was marketed at a value of $2,760,493.
Mineralization is a Ba/baryte deposit with a lenticular ore body. The baryte and witherite replace limestone associated with the slate, phyllite, and schist of the Calaveras formation of late Paleozoic age. The ore occurs in two distinct belts about 1,200 feet (360 meters) apart. Each belt strikes north and dips east. The lenses of ore, as much as 20 feet thick and 100 by 200 feet long, have sharp contacts with the enclosing isoclinally folded limestone and metasedimentary rocks. The ore is 85% barite and 2 to 3% witherite. Much of the ore is banded and retains the structure of the original rocks.
Within the baryte zone of the North Mine the rock is principally a light gray to white, granular, crystalline rock, in most places about 85-90% barite. Ore in the South Mine commonly contains 85% barite but considerable barite rock falls below that percentage and has not been considered good enough to process. A new barite ore body was discovered during diamond drilling operationsm during the winter of 1949-1950.
The deposit is cut by the west-flowing Merced River; both parts of the deposit have been mined. The deposit is truncated on the north by a small boss of granodiorite. The limestone adjacent to the granodiorite has been altered to calc-silicate rocks by contact metamorphism. Local rocks include Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada).
Workings include underground openings comprised of adits, crosscut adits and stopes. Development work included driving of a crosscut and raise on the lens-shaped ore body.
Discovered and first worked in the 1880's. The first production was recorded in 1910 and operations continued intermittently until 1914-1915. The mine operated more or less continuously from 1929 or 1930 until 1948. It has been idle since 1948. Most of the production was between 1910 and 1948, within which period 398,613 tons of barite was marketed at a value of $2,760,493.
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
3 valid minerals.
Detailed Mineral List:
| ⓘ Baryte Formula: BaSO4 Description: Bedded deposit. Occurs in a large deposit which was mined commercially. References: Brobst, D. A. (1958) Barite resources of the United States. Bulletin 1072b. US Geological Survey doi:10.3133/b1072b pages 80 (Table 9), 97, 108 (Table 10) |
| ⓘ Pyrite Formula: FeS2 |
| ⓘ Witherite Formula: BaCO3 References: |
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Pyrite | 2.EB.05a | FeS2 |
| Group 5 - Nitrates and Carbonates | |||
| ⓘ | Witherite | 5.AB.15 | BaCO3 |
| Group 7 - Sulphates, Chromates, Molybdates and Tungstates | |||
| ⓘ | Baryte | 7.AD.35 | BaSO4 |
List of minerals for each chemical element
| C | Carbon | |
|---|---|---|
| C | ⓘ Witherite | BaCO3 |
| O | Oxygen | |
| O | ⓘ Baryte | BaSO4 |
| O | ⓘ Witherite | BaCO3 |
| S | Sulfur | |
| S | ⓘ Baryte | BaSO4 |
| S | ⓘ Pyrite | FeS2 |
| Fe | Iron | |
| Fe | ⓘ Pyrite | FeS2 |
| Ba | Barium | |
| Ba | ⓘ Baryte | BaSO4 |
| Ba | ⓘ Witherite | BaCO3 |
Other Databases
| Link to USGS MRDS: | 10109245 |
|---|
Other Regions, Features and Areas containing this locality
North AmericaContinent
North America PlateTectonic Plate
- Mojave DomainDomain
- Sierra Nevada BatholithVolcanic Arc
USA
- Sierra NevadaMountain Range
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References
(n.d.) Minerals Availability System (MAS), U.S. Bureau of Mines.file ID #0060430678
Brobst, D. A. (1958) Barite resources of the United States. Bulletin 1072b. US Geological Survey doi:10.3133/b1072b pages 80 (Table 9), 97, 108 (Table 10)
El Portal Mine, El Portal, Mariposa County, California, USA