Open-File Report 2006-1259

Published 2006
Online Only

Mines, Quarries, and Other Mineralized Sites

Small mines and prospects were operated in the study area for polymetallic metals, gold, and, most importantly, pyrophyllite and refractory minerals, as well as pyrophyllite-sericite-paragonite mixtures used as coatings for asphalt shingles, as insecticide carriers, and in paint pigments and plastics.

The small abandoned polymetallic Foust Mine east of Bass Mountain (sites 454 and 1665A, fig. 2, sector B), in an area with local hydrothermal alteration (site 6716, fig. 2, sector B), and the small Robeson gold prospect (fig. 2, sector E), on a minor quartz vein, are close to the trace of the Snow Camp fault. In addition, the Snow Camp copper prospect, (fig. 2, sector E) consisting of two small shafts, is 1 mi (1.5 km) northwest of the fault. The mine and both prospects were been described by Carpenter (1976). The area along the Snow Camp fault was not sampled for soil or alluvium geochemistry, and we are unaware of any geochemical anomalies other than those at the prospects near it.

Carpenter (1976) reported that silver, zinc, and lead minerals were present on the dump of the Foust Mine. Rock on the dump consists of monzogabbro and various volcanic rocks, indicating that the mine workings crossed a plutonic-volcanic rock contact. Fine-grained dike rocks were also present. Carpenter stated that the mine was operated about 1893 and that the shaft was 78 ft (24 m) deep.

Ores were associated with quartz veins that contained pink to salmon feldspar. The sulfides observed were, in order of decreasing abundance, chalcopyrite, pyrite, sphalerite, and galena. Some secondary copper minerals were present. In addition, Carpenter (1976) reported native silver and aurichalcite ((Zn, Cu)5(CO3)2(OH)6), and minor pyrrhotite and bornite. A composite sample of sulfide-bearing rock, sample 454 (fig. 4A, sector B; table 10), contained 4,500 ppm Cu, 8,200 ppm Zn, 26 ppm Pb, 0.01 ppm Au, and 3 ppm Ag.

Gold is present at several closely spaced sites near the eastern end of Major Hill, including dumps of the Mazejka gold prospect where more copper, cobalt, and nickel are present than is normal in most sulfide veins of the area (sample 6140, table 10; fig. 3). Dump material from the prospect, several small shafts and pits, is mostly earthy saprolite and lesser hard quartz and iron oxide gossan derived from the weathered gold-bearing sulfide veins. Samples of the gossan contain visible gold, and one sample, 6140, had fresh sulfide containing 57 ppm Au. We interpret the rough alignment of workings to indicate that a northwest-trending vein or vein system was followed for at least 150 ft (45 m) by mining in the saprolite and that the workings did not penetrate much unweathered bedrock. There are also several small pits or shafts outside the northwestern trend.

A private mining company tested the locality with two exploration drill holes. No significant mineralization was penetrated by the holes drilled S. 45° E. at 45° from horizontal, but if the northwest-trending prospects indicate the vein direction, the drill holes are roughly parallel to the zone of principal mineralization and thus may have not intersected it at depth. Two types of veins are common in the drill holes, sharp-walled fractures containing fillings of quartz, carbonate, chlorite, epidote, and, more rarely, pyrite, as much as 1.5 in (4 cm) thick, and replacement veins of mostly calcite having uneven gradational walls. Unweathered wall rock penetrated by one of the drill holes was mostly gray and greenish-gray dacitic tuff, some of which was crystal rich and some of which was fragmental. Silicified rhyodacites predominate in the second drill hole. Rocks that are probably andesitic and some that are rhyolitic are much less abundant. The rocks here are mostly carbonate bearing, both as disseminations and in veins, whereas the gold-bearing rocks closely associated with high-sulfidation systems in the central North Carolina slate belt are commonly carbonate poor.

The rock samples from the waste rock dump, supplemented by soil and stream-sediment samples, confirmed the presence of gold at the prospect and at other sites nearby, and several panned samples contained significant particulate gold (fig. 5, sectors F and G). Panned concentrates D047 and D048 from a small drainage about 1,500 ft (450 m) to the south contained 23 and 35 particles visible gold, respectively (table 13 and fig. 5; D'Agostino and Schmidt, 1986).

Local residents reported old pits or shafts formerly visible in an area about 1.25 mi (2 km) east of Bethel Church, on the northern flank of the Central Highland core zone (fig. 5, sector C). To our knowledge, no trace of these workings remains. The presence of some gold there was confirmed by panned concentrates of soils and stream sediments (table 12), but the nature of the source mineralization has not been determined.

Seven or more small mines and prospects called the Zachary and Braxton Mines were opened in fractured volcanic rocks in or close to the South Fork fault system and near two felsic intrusive bodies (fig. 2, sectors K and L). Although known to local residents, this possibly important group of workings has received no mention in geologic reports and mining histories. Two Zachary mines are indicated in figure 2 (sector K), although they were not visited in our study. As some of these mines probably supplied ore to a water-powered edge-roller ("chilean") grinding mill, it is likely that operations began in the first half of the 19th century; we are unaware of mining here in the 20th century. Shear zones trending N. 30°-60° E. are common near these mines, and some have associated strong quartz-sericite-pyrite alteration. Narrow sheared and hydrothermally altered zones were common in the area around the Braxton Mine and several were sampled and analyzed. The mine (or prospect) shaft, now open to about 10 ft (3 m) depth, exposes a vertical shear zone trending N. 50° E. Volcanic rocks nearby are mostly relatively local layers of tuff, lapilli tuff, and flow rocks of dacitic composition and lesser amounts of andesitic and rhyodacitic rock. Most are porphyritic. The rock in the shear zone is sericitically altered and locally somewhat brecciated. The breccia was partly cemented by quartz and pyrite (now mostly oxidized to limonite), and most breccia fragments are less than 2 in (5 cm) in diameter. A sample of the breccia from the dump contained 11 ppm gold and 21 ppm silver (site 6064, table 10; fig. 3, sector L; D'Agostino and Schmidt, 1986).

A northeast-trending shear zone in crystal-rich fragmental dacite is exposed in the bed of Pine Branch about 426 ft (130 m) southeast of the old mine shaft (site 6063, fig. 3, sector L). Microfracturing has broken the rock along thin, closely spaced planes; these have been healed by biotite and epidote. Sample 6063, taken from the shear zone, contained 6.2 ppm gold and 14 ppm silver (table 10), but no significant amounts of other metals.

A panned stream-sediment concentrate (D072, table 13; fig. 5, sector L), taken from a western tributary of Pine Branch just south of Highway 2347 and close to the felsic pluton, contained 35 flakes of gold (D'Agostino and Schmidt, 1986).

A small shaft was opened on the top of the knob, "Ore Hill" (fig. 3, sector N), but its purpose is uncertain. Part of the quartz granofels there is magnetite bearing, and perhaps the shaft was excavated in search of iron ore. Two samples were analyzed for gold. CA84 contained 0.1 ppm, and DS83 had no detectable gold (table 8; fig. 3, sector N).

Geologic mapping included the investigation of bedrock along other strongly expressed linear features of the area. Some of these had been recognized on Landsat imagery, side-looking radar imagery, and topographic maps. Many of these linear features were characterized by pyrite-bearing sheared or brecciated zones. Four such zones, the Pine Hill Branch fault strand and three segments of the South Fork fault system to the south, were sampled at 10 sites (fig. 3 and table 10). At many other localities, rocks containing shear-related sulfide mineralization were noted in places not known to be on a major lineament. Twenty samples of these also were analyzed.

The Snow Camp pyrophyllite mine (fig. 2, sector J), now inactive, was one of the important high-grade pyrophyllite mines of North Carolina, producing about 600,000 short tons of ore from the mid-1930's to the mid-1960's (Schmidt, 1985b). The deposit, at the northern end of Mine Ridge, was mined through a deep haulage and drainage cut entering the hill from the west side. The mineralogy and geology of this mine were described by Broadhurst and Councill (1953), Espenshade and Potter (1960), Stuckey (1967), Schmidt (1985b), and Hughes (1987).

The geology of the exposed walls of the Snow Camp pyrophyllite mine is complex and difficult to interpret. Where the rock is now mostly quartz and pyrophyllite, original rock textures have been generally destroyed. In the northeastern part of the mine, however, the remaining rock in the mine walls is strongly bleached metamorphosed porphyry and breccia of uncertain relation to the quartz-pyrophyllite rock, and it may be younger than the core-zone rocks.

X-ray diffraction analyses by Hughes (1987) indicate that the alteration assemblages in the mine are quartz-pyrophyllite±kaolinite±andalusite, quartz-pyrophyllite-paragonite, quartz-chlorite-paragonite-sericite, quartz-paragonite±hematite, and quartz-pyrophyllite-chloritoid. Pyrite is locally abundant, especially below the final level of mining, which was probably close to the maximum depth of weathering. Hughes (1987) determined that some of the pyrite-rich rock in the wall of the open pit was unevenly gold bearing; the maximum gold detected was 0.43 ppm (sample 5048, fig. 3, sector J; table 8), but only 0.07 ppm was obtained in a second sampling. Many fine fractures in andalusite grains are filled by a fine-grained, highly birefringent mineral that we have interpreted to be diaspore. Rutile in small patches of amber grainlets, the grainlets less than 0.006 in (0.15 mm) in diameter, is relatively abundant, perhaps exceeding 1 percent in some samples. Lazulite, present as a showy but sparse curiosity, indicates the presence of some phosphorus; this mineral is similarly present in many of the other high-sulfidation alteration systems in the Carolina slate belt. Chloritoid is locally abundant in large scattered blocks close to the mine on the north side. Topaz has not been identified here.

The deep access road extending into the open pit from the west provides an excellent cross section of the adjacent saprolitic weathered wall rock. The change from dense, hard siliceous quartz and quartz-pyrophyllite to soft, deeply weathered metavolcanic rock, presumably Reedy Branch Tuff, takes place over only a few feet, and the plane of change dips steeply. Samples of the saprolite close to the hard bedrock and perhaps 16 ft (5 m) beneath the present soil surface had slightly anomalous tin contents (19 ppm, sample 1568, fig. 2, sector J) and copper contents (140 ppm, sample 1569, fig. 2, sector J).

A small quarry was opened near the southern end of Mine Ridge. We refer to it as the Snow Camp South pyrophyllite prospect (fig. 2, sector J). Chloritoid is locally abundant close to the quartz-pyrophyllite body; together they are enclosed in quartz-rich rock.

A trench at the Hinshaw pyrophyllite prospect was excavated in outcrops of pyrophyllite-quartz rock (fig. 2, sector N). Host rocks are altered andesitic-dacitic volcanic rocks. Most of the pyrophyllite is disseminated in quartz-rich rock, but some is present in clusters of radiating crystals in thin zones in the quartz-rich rock. Dark siliceous breccias are present here as well as fine-grained black tourmaline. No andalusite was observed.

The orebody at the Jones pyrophyllite-sericite mine (fig. 2, sector F) is in a zone of intense shearing, in a pyrophyllite-sericite rock. Unlike other commercial deposits in the area, it is not surrounded by a large zone of strong alteration, and relatively unaltered rocks, probably tuffs, are found nearby. Mineralization seems confined to the zone mined, but bedrock is not exposed along the trend of the shear zone in either direction, and the composition of the immediate host rock is not known.

The pyrophyllite prospect on Major Hill is a trench-like opening that was made on a body of quartz-pyrophyllite rock along the southern side of a large quartz-rich core zone (fig. 2, sector F). The rock surrounding the prospect is also generally pyrophyllite bearing, and it is west of an area underlain by black quartzose breccia, some of which contains chloritoid.


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