Black Rock Mining District

The Black Rock Mining District is located in the Black Rock Range.

Tingley (1998) states that other names for the area are "Hardin, Soldier Meadows, Soldier Meadow area".

Excerpts

Arnold Hague and S. F. Emmons, Vol. II Descriptive Geology, from King's Report of the geological exploration of the fortieth parallel 1877

"Black Rock Mountains.—The great Lower Quaternary plain of |he larger Mud Lake, or Black Eock Desert, which occupies, in the region included in the map, an extent of about 60 miles in a northeast and southwest direction, extending still some distance to the north beyond its northern boundary, forms the sink of Quinn's River, a considerable stream, which rises in the mountains on the borders of Nevada and Eastern Oregon, and enters this valley through a break in the Mount Very Mountains, gradually losing its water by evaporation and absorption, until, where the road crosses it near the Black Rock, it is only about six feet in width. A western arm of the desert extends a short distance north of the limits of the map, between the Black Rock and Forman Mountains, where it is shut in by the hills which connect them, while the western Mud Lake, which lies between the northern end of the Lake Range and the Madelin Mesa, practically forms part of the same plain, being separated by a low, almost imperceptible ridge of Upper Quaternary, at the southern end of the Granite Range. These plains, which during the greater part of the year are so dry and hard that a wagon-wheel or horse's hoof scarcely leaves a perceptible track upon their surface, are frequently during the winter covered to a depth of several inches with water, which must render them practically impassable, since during om' explorations in the months of October and November the occasional autumn storms had so softened the surface that mules would sink fetlock- and even knee-deep at every step, and the so-called "self-rising" portions, where the proportion of readily soluble salts in the soil is probably greater than usual, had to be carefully avoided, lest the animals might disappear altogether. Where the surface has been recently moistened by rain or spring-water, surface incrustations of soluble salts contained in the soil are found forming thin white films. Such were gathered from near the crossing of Quinn's River, and from near the so-called Hardin City, on the western arm of the desert, north of the limits of the map. They were analyzed by Prof 0. D. Allen, of Yale College, with the following result:"

"Quinn's River Salts.
Chloride of sodium 85.27
Carbonate of soda 2.59
Sulphate of soda 1.75
Water 8.57
Residue 1.82
100.00"

"Hardin City Salts.
Chloride of sodium 18.47
Carbonate of soda 52.10
Sulphate of soda 27.55
98.12'

"Of the latter, Professor Allen says: 'It is reasonable to suppose that it contains an appreciable amount of borate of soda.'"

"The general level of the Mud Lakes is about that of the lowest part of the Humboldt and Carson Deserts, from 3,850 to 3,900 feet above sea level, while similar terrace-lines attest the former presence of the waters of the La Hontan Lake. The terrace-lines are in general more distinct on the western side, where a steeper wall was presented to the former lake, and later erosion has not so readily concealed them. Deposits of lacustrine tufa are abundant in the Black Rock Mountains, covering some of the lower outlying hills and extending through the lower passes. They are also found along the slopes of the Granite Range, and in greatest development along the basalt wall of the Madelin Mesa on the western side of the smaller Mud Lake."

"The Black Rock Mountains form topographically a southern spur of the mountain mass north of the limits of the map, whose culminating point is known as Mount Lander, a peak of apparently 9,000 or 10,000 feet in height, which is probably connected with the northern continuation of the Granite Range uplift. The portion represented on the map consists of low broken ridges of rhyolite and basalt, in which these rocks are found quite regularly bedded, and presenting almost uniformly a bluff face to the west, with a gentle slope to the eastward, their bedding planes having as high an angle as 20°. As a rule, the basalt flows form the summit of these ridges, while on the western bluff faces are found, at the base, the outcrops of underlying rhyolites. In a few instances, however, rhyolites were found again, forming the capping beds, generally separated, it is true, by intervals of debris slopes from what appeared to be the underlying basalt flows. It seems probable that the present structure, and perhaps, also, the apparent superposition of rliyolite over basalt, is due to a general faulting and fracturing of the beds at tlie time of, or since the outflow of the basalts, and that in the one instance observed, where rhyolite seemed actually to overlie basalt, the latter might have poured out between previously formed rhyolite beds, as undoubtedly occurs at times in sedimentary rocks."

"It is interesting to observe in this connection that the abundant hot springs which occur in these hills are almost invariably found on the edge of the desert along the western foot of the mountains. Of these, the group of Warm Springs, locally known as the Double Hot Springs, about 6 miles from the southern point, consists of two adjoining pools about 15 or 20 feet in diameter, and apparently about as many deep, with other smaller pools in the vicinity, from all of which there is only a small overflow of water. The water has no perceptible taste, but it has a very high temperature, that of the larger pools at the surface being 165° to 168° F., while one of the smaller pools gave a temperature of 171° (78° C). Probably below the surface the temperature is very near the boiling-point."

"This region possesses a weird interest, not only from its peculiarly desolate physical character, being, with the exception of the hot springs above mentioned, entirely without water, and utterly devoid of vegetation, not even supporting a growth of the almost ubiquitous sage-brush (Artemisia tridentata), but also from the large development of the more unusual accompaniments of volcanic rocks: concretions and.geodes of chalcedony and agate are present in great quantity and of most varied forms and colors, while the occurrence of a persistent bed of decomposed basalt, perfectly honey-combed with amygdaloidal cavities filled with green earth, the fissures of the more compact portions being covered frequently with a thin dendritic coating of oxide of iron, has been the cause of leading hundreds of ignorant but enthusiastic miners into the belief in the presence of valuable argentiferous minerals. At the time of our visit in 1867, this belief, fostered by fabulous reports, spread abroad in part by ignorant, in part doubtless by designing, persons during a series of years previous, the fear of hostile Indians and the inaccessibility of the region rendering trustworthy accounts difficult to obtain, had culminated in the establishment of a mining-town, called Hardin City, just north of the limits of the map, near some springs on the edge of the desert, and the building of two small mills, to work the so-called ore. Had the vein, this bed of decomposed basalt, been metal-bearing, it might have been the source of untold wealth, since, with a thickness of 40 to 60 feet, it could be traced almost continuously over an extent of thousands of acres; but a careful chemical examination revealed, as might have been expected, no metal other than a small percentage of iron."

"The extreme southern point of the mountains is a rounded hill, rising about 500 or 600 feet above the desert, formed entirely of basalt, which, from the contrast of its blackened weathered surface with the white desertplains, has received the name of Black Rock, afterward transferred to the whole ridge. It is composed of a fine- grained rock, on freshly broken surfaces of a greenish-gray color, a conchoidal fracture, and sometimes rather granular texture, showing small crystals of fresh plagioclase and abundant yellow-brown augites ; it contains also considerable calcite, which fills crevices, and sometimes forms minute crystals in the mass. From a little hill just north of this, at the southern end of the main ridge, was obtained a remarkably interesting dolerite, which was found alternating with a reddish, porous, fine-grained basalt. The dolerite is remarkable for its large tabular crystals of plagioclase, sometimes an inch in diameter. It is of a dark greenish-gray color, and resembles that found at the southwest end of the Kamma Mountains, but is much more coarsely-grained, and has a somewhat resinous lustre. In it can be distinguished crystals of dark-brown augite up to one-fourth of an inch in diameter. Under the microscope are detected, besides plagioclase and augite, olivine and magnetite, but no sauidin, quartz, or titanic iron. The crystalline ingredients are generally very fresh and unaltered, and a little amorphous base, in the form of wedge-shaped grains between the crystals, is present. Basalt forms the mass of the hills for some distance north of the Black Rock. Among these basalts was found a deposit of basaltic tufa, a loose; gray, fine-grained mass, not to be distinguished by the unaided eye from that observed in the Pah-tson Mountains, but which, under the microscope. is seen to be made up, with the exception of some tabular crystals of feldspar, of fragments of the hyaline volcanic glass, called palagonite. The occurrence of palagonitic tufa here is particularly interesting, as being the only occurrence found, not directly connected with the Tertiary beds of the Truckee Miocene."

"The rhyolites were principally examined in the neighborhood of Hardin City, where the mountains are wider than at the southern point, and the peculiar structure of the hills already noticed more prominent. These rhyolites are generally of earthy and brecciated varieties, and poor in crystalline secretions. Their groundmass is characterized microscopically by a medium character between the indistinct and the microfelsitic, as is shown in Vol. VI, Plate VII, fig. 1."

"At the base of the cliffs east of Hardin City are outcrops of white loose-grained rhyolitic breccias, having a gravelly structure, and containing small pebble-like fragments of darker- colored rhyolites in a white felsitic groundmass. They have an appearance of bedding, and are exposed in a thickness of several hundred feet, showing varieties of texture, from the loose crumbly nature above described to a tolerably compact mass, having, however, the same gravelly composition. Above this occurs the so-called Snowstorm Ledge, a bed of decomposed basalt, from 40 to 60 feet in thickness. In its extreme form, this basalt is a greenish-drab earthy mass, rendered almost like a sponge by the quantity of amygdaloidal cavities running through it, which are generally filled with a green earthy powder. Where the decomposition has not proceeded so far, the basalt is of a light greenish-gray color, showing no macroscopical crystalline ingredients, its mass still full of smaller or larger rounded cavities, some of which are filled with the green earth, others again lined with botryoidal concretions of chalcedony, and in others still the botryoidal form is preserved, but a thin coating of hydrous oxide of iron only remains. The top of the cliff is made up of a fresh, black, lustrous basalt, with clean conchoidal fracture, ringing under the hammer, and of fine, even-grained texture; this has also irregular crevice-like cavities, lined with a botryoidal coating of chalcedony, and in some cases containing a little calcite. On the slopes of the adjoining hills and ravines are innumerable geodes, lined generally with quartz crystals, and sometimes disclosing agates of great beauty. The green earth filling the pores of the decomposed basalt, being tested chemically, was found to consist principally of silica and alumina, Tvith some alkalies, and a small percentage of iron. It is probably what is generally called seladonite. Microscopical examination of these basalts confirms the conclusions drawn from their external appearance. They are seen to be much altered, the magnetite is changed into yellow hydrous oxide of iron; there are no distinct olivines; the augites are pale and scarce; in the green powder is found titanic iron, which, when fresh, cannot be distinguished from magnetite. The peculiar structure of the augite-microUtes is shown in Vol. VI, Plate I, fig. 19."

"The highest point in this region, a little north of the bluffs above described, called Hardin Mountain, is capped by a light mauve-colored rhyolite, containing, in a rather porous felsitic groundmass, crystals of sanidin and quartz, and fragments of white and yellow pumiceous rhyolites. On the eastern flanks of this hill were found other outcrojjs of decomposed basalt, and in a ravine called Star Canon, running east and west across the mountains, at a considerable distance to the eastward, similar successions of basalt beds dipping eastward, underlaid by a variety of rhyolitic breccias, and in one case overlaid by a reddish, earthy, rhyolitic breccia. A rounded hill on the eastern borders of the mountains, known" as Utah Hill, consists of a breccia-mass of hard flinty rhyolites containing free quartz, with very little cementing material between the fragments."

"Among the interesting occurrences in this region is to be mentioned a deposit of pisolite, which is found as an incrustation round a spring in these mountains, about 15 or 20 miles north of the limits of the map. The specimens, brought in from this place by the miners, are aggregations of grains about one-fourth to three-eighths of an inch in diameter, perfectly white, of concentric structure, but having the form of very regular pentagonal dodecahedrons, which may possibly be a result of contraction or mutual compression. From the Forman Mountains, to the westward, was brought also a curious light-gray i-hyolitic rock, interesting on account of its peculiar columnar structure, the columns being about an inch in diameter, and made up of an aggregation of very perfect little hexagonal prisms about an eighth of an inch in diameter each. The only crystalline ingredients visible are a little free quartz and a few feldspars."

"The Forman Mountains, as represented on the map, are the southern point of a range of mountains, in which both these and the Black Rock Mountains are probably merged to the north. They were only examined opposite the Cold Spring, a large spring of fresh cold water on the edge of the desert, near their southern point. Here they were found to consist exclusively of rhyolitic rocks, in Avhich, as at Black Rock, the breccias play the most important role. Of the specimens of rhyolite obtained, one is a pure white felsitic mass, of conchoidal fracture, containing only white, halfkaolinized feldspars, with no other crystalline ingredients. Another variety is a reddish porphyritic rhyolite, with rough fracture, containing well-defined glassy sanidins, sometimes in Calsbad twins, and free quartz in a compact felsitic groundmass. With these occur breccias, which closely resemble the parent rock, being in no way distinguishable from it except from the fact that it shows a combination of angular fragments, all of the same composition and color, which is also that of the material which binds them together. Another white porous breccia is seen, however, to contain strange fragments of dark slate color, apparently of some older rock, which are too homogeneous, however, to offer definite cliaracteristics."

References from Tingley

• Stretch, 1867, p. 46.
• Territorial Enterprise, March 7, 1868.
• Angel, 1881, p. 450;
• Bancroft, 1890, p. 103.
• Stoddard, 1932, p. 44.
• Gianella, 1945, p. 76. Soldier Meadows nitrate area.
• Garside, 1973, p. 56. Soldier Meadow uranium area.
• Carlson, 1974, p. 220.
• Papke, 1979, p. 21.
• Wheeler, 1979, p. 139.