Herbb No. 2 Mine, Flat Rock, Powhatan County, Virginia, USAi

Regional Level Types
Herbb No. 2 Mine	Mine
Flat Rock	Unincorporated Community
Powhatan County	County
Virginia	State
USA	Country

"The Herbb No. 2 mine, also in Powhatan County, is 3.6 miles (ca. 6 km) northeast of Flat Rock and 0.45 mile (ca. 724 m) north-northwest of the Herbb No. 1 mine (location 23, pi. 72). The workings are dragline excavations that were made during the spring of 1944 by Colonial Homes, Inc., of Richmond. At least four deep trenches were dug across the pegmatite body, and a fifth follows it in a northerly direction. The two southernmost trenches were partly obliterated by a later cut, which is 125 ft (ca. 38 m) long, 20 (ca. 6 m) to 40 ft (ca. 12 m) wide, and 20 ft (ca. 6 m) in maximum depth (fig. 72).
The pegmatite body, which appears to be an elongate lens that cuts the foliation of the enclosing schist, trends north-northeast and dips east-southeast in the pit, where it is 4 (1.22 m) to 25 ft (ca. 8 m) thick. It is about 45 ft (ca. 14 m) in maximum outcrop breadth at the north end of the pit. In the northernmost trenches its walls converge rapidly downward, and its keel probably is very near the surface (section A-A' fig. 72). This keel may well plunge gently south; hence its surface trace may not be far north of the workings.
A large inclusion or septum of schist is exposed at the north end of the pit (section B-B'}, but its surface relations are obscured by piles of dump material. The foliation of the thoroughly weathered biotite schist country rock dips rather gently.
The pegmatite is mineralogically complex, and, though not well enough exposed for systematic detailed study, appears to be strikingly similar to the Morefield and Rutherford pegmatites in Amelia County. A discontinuous core of massive quartz lenses 1 (ca. 30 cm) to 5 ft (1.52 m) thick and 10 (ca. 3 m) to 25 ft (ca. 8 m) long is surrounded by an intermediate zone of coarse, blocky green perthite (amazon stone) and flesh-colored to reddish perthite. The wall zone, which is 2 (ca. 61 cm) to 4 ft (1.22 m) thick, appears to have been a medium- to coarse-grained aggregate of perthite, quartz, and possibly plagioclase. Much of this material, however, has been corroded and almost completely replaced by albite, which occurs as fine-grained, sugary-textured aggregates and as clusters of platy cleavelandite crystals. The distribution of the late-stage feldspar appears to have been governed by fractures, cleavage cracks in perthite crystals, and cracks between individual mineral grains, but kaolinization is too thorough to permit detailed study of the relations in most places.
In the potash feldspar of the intermediate zone, which is distinctly less weathered, the fracture control of the distribution of albite is very plain.
Mica, garnet, and beryl occur in partly albitized perthite, especially adjacent to the quartz masses. The prismatic beryl crystals are as much as 27 in. in diameter and 59 in. or more long. Most are more than 5 in. in diameter, and all have some faces that bear impressions of cleavelandite crystals. Small, lustrous, tabular to equant crystals of columbite-tantalite are scattered through the albitized wall-zone pegmatite and are particularly abundant along the hanging wall opposite the northeast quartz mass in the pit.
The mica is pale yellowish-green to cinnamon-brown material of poor quality. "A" structure is common. Many of the books are soft, buckled, broken, and clay-stained. The majority are small, although a few as much as 14 in. in diameter were noted. Some sheets can be trimmed from the flat parts of the larger books, but the recovery is extremely low. A little sheet mica, several tons of scrap, and about 2 tons of beryl are reported to have been obtained during the mining. The deposit appears to have some commercial possibilities as a source of feldspar, with beryl and scrap mica as byproducts."