Custer Mine, Darwin – Collection Site 4
Custer Mine, Darwin – Collection Site 4
Custer Mine, Darwin, Darwin District, Darwin Hills, Inyo Co., California, USA
A former Pb-Ag-Cu-Zn-Au mine located in sec. 19, T19S, R41E, MDM, 1.6 km (1.0 mile) ENE of Darwin, in a narrow canyon, locally called Custer Canyon. The road is washed out and one has to hike down the canyon. It was in operation from the 1870’s until the 1950’s, but with long idle periods. It was re-timbered in the early 1950’s, but operation was closed down a few years later. MRDS database stated accuracy for this location is . Corrected description and position N36.27317 W117.57432 by Richard Muster, courtesy Gail Dunning, Walt Margerum and Robert Hously.
Mineralization is hosted in tactite. The ore body is pod-shaped and lies on the contact between a dark brown calc-hornfels and a body of blue-gray limestone and is hosted in an irregular body of crystalline calcite. Local rocks include Carboniferous marine rocks, unit 2 (SE California Carbonate Assemblage) and/or Quaternary alluvium and marine deposits.
Workings include underground openings comprised of 2 separate workings. The main working consists of an inclined shaft on the N side of Custer canyon with a depth of 400 feet and with levels at 50, 200, 250 and 300 feet. A wince extends another 240 feet. The minor part consists of an adit, approx. 125 feet long, which was driven in the 1950’s into a mineralized copper-lead-zinc contact zone that occurs on the south side of the canyon. No viable ore reserves were found and this operation was ended.
Most of the minerals interesting for collectors come from this adit with the approx position of N36.27259, W117.57362. Entry was possible without restriction and dumps were accessible in 2003.
Production data are also found in: Goodwin, J.C. (1957): 465.
It produced until 1949 approximately 141 ounces of Au, 17,000 ounces of Ag, 6,600 pounds of Cu, 97,000 pounds of Pb and 72 pounds of Zn. 50 tons of ore were shipped in 1940-1941.
|The report by Hall and Mackeverett on the Darwin area gives an overview of the geology of the Darwin Quadrangle and if you can obtain a copy of Hall, W.E., and Mackeverett, E.M., Economic Geology of the Darwin Quadrangle, it is well worth pursuing.
The mines in Custer Canyon include the Custer, Custer adit and St. Charles Mines and the Lucky Lucy Prospect. The next canyon south contains an interesting group of lead-silver- tungsten mines, the Durham-Fernando Mine being the largest.
Custer Canyon is located about 1 mile east of Darwin in the first canyon south of Zinc Hill Road. It is known locally as Custer Canyon although the name does not show up on most of the maps of the area. While a road is shown going down the canyon, it appears to have been washed out by a flash flood. Only the lower portion is passable if accessed from the bottom. The mine is in section 19, T. 19 S., R. 40 E., M.D.M. at latitude 36o 16¹ 20² North and Longitude 117o 34¹ 20² West on page 40 of Delorme¹s Southern and Central California Atlas and Gazetteer. A mine is shown on the map but is not named. Since the Custer Mine and the nearby St. Charles Mine share the same dump they essentially look like a single mine though they are actually two separate mines and had completely different ore mineral suites.
The St. Charles Mine
The St. Charles Mine is located in a tactite body that was formed at the contact between a quartz diorite and the Lost Burro Limestone. It has been extensively fractured and several intersecting minor faults cut the ore body. The ore was unusual because much of it consisted of veins of massive scheelite that could reach as much as two inches thick. These veins were usually encased in a tactite with a higher than normal garnet content.
The tactite is on an extension of the Custer vein system, but unlike the led-sliver ore body at the Custer Mine, the St. Charles Mine is situated at the top of a tungsten ore body. The tactite there is composed principally of massive green to brown andratite garnet but also contains veins of yellow-green massive epidot with small pockets of epidot crystal.
Sulfides were not common in the tactite and pyrite was the only sulfide found in the upper portion of the mine. The pyrite crystals can reach up to 1/2 inch and cubes are the most common form present. The crystals are typically heavily striated on the faces and occur in calcite filled cavities in the tactite. These pyrite crystals are often encased in calcite and when the calcite is removed they make attractive specimens.
The St. Charles Mine is developed by three separate workings.
Bismuth Sulfosalt Complex
The major production at the St. Charles Mine was during the 1950’s, but by 1955 the ore bodies were exhausted and the mine was abandoned. When the price of tungsten went back up in the ’60, the mine was briefly reopened but failed to produce any signifient amount of ore and was closed. The claim is presently inactive, though sporadic exploration work has taken place over the years.
The Custer Mine
The Custer Mine is the next mine of any importance found as you continue down the canyon. The Custer Mine is composed of two separate workings. A shaft over 400 feet deep represents the major working while a tunnel was driven into a mineralized lead-zinc contact zone that occurs on the south side of the canyon.
The Custer Mine was first worked during the 1870¹s when Darwin boomed and produced considerable rich high-grade lead-silver during this period. The rich ores were mined out after a few years and the Custer Mine went into decline along with the rest of the Darwin District. The mine was abandoned until 1950 when several of the Darwin mines were consolidated and reopened along with the Custer Mine. It was retimbered and additional mining carried out in the deep levels of the mine. The inclined shaft which was the major access ultimately reached a depth of over 400 feet and levels were driven at 50, 200, 250, 300 and 400 feet. The upper levels above 250 feet dated from the original days of operation and little ore was found there in the later efforts.
The Custer Adit was driven into the south wall of Custer Canyon to explore a showing of copper and zinc minerals. The tunnel is about 125 feet long and was dug during the 1950¹s in hopes of finding new ore reserves. Although oxidized zinc ores were found no mixable ore reserves were found and the operation was ended.
The Main Mine
|Goethite psudomorphs after Pyrite
The Custer Mine and the Custer Adit were last worked in the early 1950¹s and when the Darwin Mines closed the Custer Mines also ceased production. When the mine closed, all activity ceased and the mine was abandoned. Entry appears to be possible without restriction and the dumps are readily accessible.
The Lucky Lucy Prospect
The Lucky Lucy Prospect is located on the northern slope of the canyon about 100 feet northwest of the Custer Mine Shaft. It is a small pit that was worked in the 1950¹s when the larger mines in the area were working. Once the small copper-zinc ore body was mined out, the prospect was abandoned; the claim is now abandoned.
The Lucky Lucy Prospect is situated in a portion of the tactite body that formed at the contact between a calc-hornfels and the Lost Burro Limestone. A quartz monzonite outcrops nearby, although this feature appears to have had little relationship to the ore body that was formed. The tactite body was fractured by local fault movement and the ore body was formed as a replacement of the tactite.
The Lucky Lucy Prospect is one of those curious anomalies that make mineral collecting so interesting. It is completely different from the nearby mines and the minerals it contained were distinctly different. The brochantite and serpierite were well crystallized, and the serpierite find represented the first California locality for this rare and unusual mineral.
The ore body was unusual in the fact that, in an area of lead-silver and tungsten mines, the ores were predominately copper and zinc. The ore body consisted mainly of a mass of hemimorphite and chrysocolla. Sulfides occurred only as relict pieces. Specimens of chalcopyrite and sphalerite have been found on the dump, but galena was completely absent. While the bulk of the oxidized ore was silicates, a band of sulfates occurred near the edge of the ore body. Excellent specimens of brochantite and serpierite were found in this area and on the dump.
A specimen of the unusual tungsten ore bearing an the bismuth sulfosalt complex mentioned above was found on the Lucky Lucy Prospect dump. It closely resembles the ore found in the deep Levels of the nearby Custer Mine and the nearby St Charles Mine. But as no ore of this type was noted underground at the Lucky Lucy Prospect, it may be a manuport from the Custer or St. Charles Mines.
Probably the best specimen material found at the Lucky Lucy Prospect was a group of sulfates from the periphery of the ore body that contained a number of unusual oxidized copper-zinc minerals.
Goethite & other olidized minerals
All in all the Lucky Lucy Prospect was a fascinating place to collect. I just wish that they had left more of the leaner ore around.