| Willis Mountain | |
|---|---|
 | |
| Highest point | |
| Elevation | 353 m (1,158 ft) |
| Prominence | 350 m (1,150 ft) |
| Coordinates | 37°28.3439′N78°27.4920′W / 37.4723983°N 78.4582000°W /37.4723983; -78.4582000 |
| Geography | |
| Location | Buckingham County,Virginia |
Willis Mountain is amonadnock rising from the rolling hills of thePiedmont province of Buckingham County, Virginia, a little east of the geographic center of the state.[1] Willis Mountain is located about 6 mi (9.7 km) southeast ofBuckingham, Virginia, and 18 mi (29 km) northwest ofFarmville,Prince Edward County. In a general north-south direction, U. S. Highway 15 borders the western side of the mountain.[2]
Willis Mountain consists of a narrow ridge that is about 2 mi (3.2 km) long, with steep rocky slopes. Near its center, it is broken into two segments by a lowsaddle. Southward of the saddle, this ridge rises to an elongated knob known locally asRound Mountain with an altitude of 1,150 ft (350 m). Northward of the saddle, this ridge rises to an altitude of 1,159 ft (353 m), which is about 500 ft (150 m) above the adjacent valley floor. Second-growthtimber, mostlyhardwood and somepine, cover the sides of Willis Mountain. Afire lookout tower occupies thehighest point of Willis Mountain.[2]
Willis Mountain is well known as the site of a large deposit ofkyanitequartzite that has been actively mined for kyanite for decades. This deposit is the largest of five large kyanite deposits that occur within a 7 mi (11 km) wide belt known as theWillis Mountain kyanite-quartzite belt.[2]
The landscape of Buckingham County surrounding Willis Mountain is typical of the Piedmont Plateau within Virginia. The landscape consists of gently rolling broad, flat-topped ridges separated by narrow valleys. A low relief network of streams within these valleys allow for rapid drainage. A deep mantle of highly weatheredbedrock, calledsaprolite underlies the surface, except where the larger streams have carved deep valleys. Except monadocks like, Willis Mountain, the ridge crests are consistently uniform in elevation, ranging from 450 ft (140 m) high in the eastern portion of the area to 550–600 ft (170–180 m) high in the eastern portion of the area. Willis Mountain rises above the level of thesr surrounding ridges as a solitary monadnock to an elevation of 1,159 ft (353 m).[1][2]
Willis Mountain rises above the surrounding countryside because the massive deposits of kyanite quartzite underlying it are highly resistant toweathering in the regional climate. Unlike themetamorphic bedrock underlying the surrounding countryside, the kyanite quartzite lacks the thick cover of saprolite. Instead, the kyanite quartzite characteristically is well exposed as ledges, where it is thinlyfoliated with lowdips, to forming bold crags and cliffs of Willis Mountain. These weathered ledges, crags, and cliffs are rough and jagged because the grains of quartz are more easily eroded than the large crystals of kyanite. The ledges, crags, and cliffs exhibit deeply etched pits and furrows because of differential weathering alongfoliation,joints, and linear rock structures. The weathering ofpyrite within the kyanite quartzite has heavily stained and impregnated the exposed bedrock withlimonite.[3]
The western limb of north-south trending Whispering Creekanticline underlies Willis Mountain. It and Round Mountain are supported by a westward dipping stratiform layer of kyanite quartzite within the west limb. The kyanite quartzite is overlain and underlain by quartz-muscoviteschists. The schists are enveloped bybiotite-amphibolegneiss of theCambrian Chopawamsic Formation. An eastward dipping layer of kyanite quartzite within the east limb of the Whispering Creek anticline forms a lower and longer ridge that lies east of Willis Mountain.[3][4]
The kyanite quartzite and associated schist and gneiss consist ofvolcaniclasticsediments andvolcanic rocks that have been altered byamphibolite grade metamorphism under pressure as high as 6.5 kb and temperatures as high as 600 °C. The interpretation of isotopic, trace element, and other data and mineral equilibria suggest that the kyanite quartzite was created by themetamorphism of highly altered intermediate volcanic rocks. Prior to metamorphism, the original volcanic rocks had beenhydrothermally altered by acidic fluids (pH 2 to 4) at temperatures between 100 and 200 °C under mildly oxidizing conditions. Alumina and silica also had been residually enriched by rockhydrolysis during the hydrothermal alteration.[5][6]
The kyanite deposits of Willis Mountain was first reported by David Campbell in 1839.[7] These deposits were later investigated by the Virginia Geological Survey in 1932[8] and by the US Bureau of Mines in 1949 and 1950.[2] The Kyanite Mining Corporation purchased the main ridge of Willis Mountain and began mining the south end of it in 1957.[3]
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