Nightingale Mining District

By webmaster at 12:36 pm on June 16, 2008 | No comments

A nice mineral collecting day trip from the Reno area is to the Nightingale Mining District, an area with many mines and interesting geology, flora and fauna. The area produced mostly tungsten with some by-products but has not been significantly active since the demand for the metal declined after the Korean War. There are a number of major mines with associated ruins as well as hundreds of smaller prospects. As with all such areas, approach any mining area with caution. Do not enter mine openings and remember that not all shafts and pits are fenced.

We approached Nightingale from the southwest from the south end of Pyramid Lake and the town of Nixon. Pyramid Lake is one of the largest and deepest desert lakes in the Great Basin; is is one of the remnants of the huge Lake Lahontan that covered thousands of square miles in northwestern Nevada several thousand years ago. From Nixon a gravel road trends north and east crossing a divide to the basin of Winnemucca (dry) Lake. This lake bed is long and narrow and parallels the Nightingale Mountains on the west. Our goal was the MGL mine, some 7 miles north of the main access road and a mile or two up into the mountains.

tufa and lakebed
The road north passes some spectacular volcanic geology and excellent examples of ancient shorelines with associated tufa mounds. in several areas old beach deposits consist of hard, cemented gravels made up of black eroded igneous rocks that flank the basin in the area.

At the lower end of the canyon where the MGL Mine is located is the cement foundation of the processing plant where tungsten ores were concentrated. The ores were crushed and the heavier minerals containing tungsten were separated and concentrated during several stages of processing as they traveled down through the mill. Concentrates were hauled by truck to a railroad for transport to refining plants outside the area.

mgl mill foundation
The road up the canyon required a bit of careful driving and would not be passable in wet weather. The ore chute or dump is located below the main mining operations. Open cuts in the tungsten bearing rocks can be seen above it. There are several adits (horizontal tunnels) that access the ore zones and allow the ores to be moved down and out to be loaded on trucks for the trip down-canyon to the mill.

mgl ore chute and mine

The dumps around the ore chute and along the access roads contain many of the minerals that can be found in the open pits and tunnels. The MGL Mine is known for particularly fine specimens of large, brown andradite garnets as well as clinozoisite. Some of the best examples can be etched from calcite that fills some veins and pockets, protecting the crystals. Other minerals include pyrite, quartz, tremolite, copper secondary minerals and rare molybdenite.mgl open pit/garnet area

Although the area is dry this time of year there are a variety of flowers and lots of lizards. Desert plume, Stanleya pinnata, is one of the more spectacular. Lizards like the black-collared, the western whiptail and the sagebrush lizard abound. It must have been a productive spring for them, because there were little lizards everywhere. It is amusing to see a 3-inch lizard on a 6-inch rock, protecting his territory with all of his bravado. The bigger lizards get to protect bigger rocks, and even graduate to a boulder if they are really assertive. And they run like the wind! Even the littlest ones will raise a small plume of dust as they dash down the road.

mgl garnet clinozoisite

desert plume

Returning to the main access road we again went northeast over a pass of about 6,000 feet in elevation to the site of the Nightingale Mines. Here are cement foundations and a metal stack and a large water tank that provided water for the milling operation. Most of the metal structures have been riddled by bullet holes and there is considerable trash left by campers. I have never thought of a water tank as a challenging target, but it must be.

lizard hanging out

The mining here was concentrated in a steeply-dipping sedimentary unit some 15 to 20 feet thick that has been metamorphosed by nearby and included granitic intrusives. The mining covers some half-mile of strike and has left large, open cuts and overhangs. Dumps contain a similar assortment of minerals as seen at the MGL Mine, but the rock is ‘tighter’ with less opportunity for good specimens where we checked.

black collared lizard
Returning over Nightingale Pass we stopped at some smaller workings known as the Jay Bird Mine but found nothing of interest. The rest of the trip was uneventful. Pyramid Lake was calm and some the local white pelicans were having a meeting on the beach as we passed by. All in all a very good day.

Nightingale mine openings

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S.E. Colorado Barite

By webmaster at 1:30 pm on May 14, 2008 | No comments

In the early and mid 1970’s I spent several months working on the uranium potential of the Denver Basin and, in particular, the area east and southeast of Colorado Springs and Trinidad. We were evaluating mostly Lower Cretaceous rocks but spent some time checking surface and sub-surface anomalies based on areal and ground water sampling programs. Surface rocks in much of this area consist of Upper Cretaceous shales containing multiple horizons with large concretions.

On a late afternoon in 1972, returning to our base of operations in La Junta from the area near Timpas, we stopped to check a shale unit along the highway and found several promising concretions. We excavated one, about 4′ in diameter, and found what may have been the first reported clear barite in what was later called the “La Junta” barite area. These barites are often water-clear and display a variety habits some of which are remeniscent of those found in concretions near Grand Junction.

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The specimen pictured was displayed at the Denver Gem and Mineral show in, I believe, 1976 in a Self-Collected Minerals case. The blocky crystal is about 2.3 cm on an edge. It generated a bit of interest and the location was given to several people, including Don Knowles who reported little success after at least one trip to the area. Some years later I received an inquiry from Dan Kyle about the location and sent maps of the area to him. As most collectors in the Denver area know, Dan has found some very fine specimens there.

While much has been said about the clear barites there are two additional locations that I have always wanted to re-visit. One, not far from the original barite discovery, was near a well where we collected a water sample. Weathered concretions on the surface nearby contained lovely rosettes of white, flattened calcite rhombs up to 3 inches across displayed on a matrix coated with orange-brown lichens. Another, some miles to the east, was a somewhat obscure zone of smaller concretions, up to about 2.5-3 feet in size, with tabular blue to blue-gray and yellow zoned barites up to 2 inches on a calcite-crystal matrix. We spent less than 20 minutes walking contour on this concretion zone and found one weathered open, with the crystals described above and several others that looked promising but we did no digging.

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Mclaughlin Mine, stibnite

By webmaster at 4:30 pm on April 8, 2008 | No comments

In the early 1980’s development work at the Homestake Mining Company Mclaughlin Mine project at the junction of Napa, Lake and Yolo counties in California turned up some nice stibnite specimens. Drill core from some areas contained scattered stibnite in veins and vugs, and in one case, stout crystals up to 3-8 cm in a wide calcite vein. The best specimens from this period, however, were found when a bulk sample decline was sunk in a near-surface part of the ore body. This work was designed to sample an area of the silicified Knoxville formation mudstone, a significant gold host on the property. Numerous quartz-chalcedony veins in the workings contained stibnite in masses, radiating sprays and in small vugs. The best specimens showed bright, needle-like sprays up to 3 cm in open vugs lined with bright micro quartz.

The muck (bulk sample) piles provided lots of fine samples, sometimes in masses of radiating crystals up to several pounds. The exposed faces in the decline were great for finding vugs, but were dangerous and usually only accessable after a blast when the fumes were sure to cause a nice ‘nitro’ headache. A contract minor was severely injured by rockfall at the working face during this period.

There are still a few of these specimens around; there should have been a lot available from the pit as it progressed, but I only have a few remaining. One is pictured here.

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