[Sheet of mica]

Mica

Micas are a very common rock-forming mineral and can be found in every county in the Blue Ridge and Piedmont provinces. Micas occur as flakes or scales in many igneous and metamorphic rocks and to a much lesser extent in the Coastal Plain sands. Micas are more notable when they occur in pegmatites. Pegmatites form during the last stages of emplacement of granitic igneous rock and contain fluids rich in rarer elements and cools very slowly so the crystals grow larger than usual. Therefore, pegmatites often have larger crystals and contain rarer minerals.

Map of Mica Resources in North Carolina

History and production

The history of mica is directly tied to the history of feldspar production and past mining of kaolin in the Blue Ridge since these are associated minerals. Evidence of old mica mining was reported by geologists in 1875 and 1876. They noted numerous prospect pits dotting the hillsides, some of which were very extensive in size with trees, 3 foot or more in diameter rooted on large spoil mounds next to the pits.

Mica has been actively mined in North Carolina since the mid-1800ís. Large sheets of muscovite were hand cobbed from rock to be used to make windows in stoves and furnaces. Later, sheet mica was used as an electrical insulator in electrical apparatus such as toasters and electrical sockets and in vacuum tubes. With the advent of WWII, mica supplies from Europe were cut off so the Mitchell-Yancey-Avery county area became one source for mica for use in electronics. In the early 60ís with the development of solid state electronics, the Federal government stopped buying sheet mica and many mines closed. Today most of the mica produced is scrap or ground mica, a coproduct from feldspar production.

Map of Mica Occurrences - Spruce Pine District

Ground mica has been in roofing felts and shingles. Presently it is used as a mineral filler in paint, plastics and wallboard.

In the Spruce Pine District of Mitchell, Avery and Yancey counties there are over 700 mines recorded that produced mica and/or feldspar. There is probably 2 to 3 times as many prospects or borrow pits in the area. Listed below in the occurrence section in the mineral descriptions, are a few collecting sites in Mitchell County and one in Yancey County that are relatively safe and easy to get to in these counties. (See Section on Mineral Collecting Protocols).


MINERAL DESCRIPTIONS

Muscovite (white mica)
Chemical
Composition
KAl2Si3O10(OH)2, Potassium aluminum silicate.
Class Silicate
Crystallography Monoclinic; prismatic
Habit Crystals usually tabular with pseudohexagonal outline; commonly lamellar massive and
small flakes. In plumose (featherlike), stellate, or globular forms; scaly massive; also
compact massive and cryptocrystalline.
Physical
properties
Cleavage {001} perfect; sometimes shows parting parallel to {010} and {110}.
Cleavage laminae flexible and elastic. H. 2.5 on cleavage surface, 4 across cleavage.
S.G. 2.77-2.88. Luster vitreous, pearly, or silky. Transparent and colorless in thin
sheets. In thicker blocks translucent, with light shades of yellow, brown, green, red.
Streak white.

Map of Mica Mineral Localities

Mineral localities and descriptions of localities are from Wilson and McKenzie (1978) and Conley (1958). These locations have not been field checked for accuracy, minerals present or for accessibility. The site code (e.g. AVERY-002) refers to the site reference in the Mineral Locality Index.

Occurrences

Muscovite is a very common rock-forming mineral and can be found in every county in the Blue Ridge and Piedmont provinces. It can be found in many igneous and metamorphic rocks and to a much lesser extent in the Coastal Plain sands. It is more notable when it occurs in pegmatites where it can be very large in size.

Ashe County The Duncan mine (abandoned), 1.2 miles southwest of West Jefferson was worked for mica and it also contains beryl (ASHE-001).
Caswell County A pegmatite dike (crosscutting) 10 to 12 feet wide is exposed in a road cut on the north side of SR 1554, 0.35 miles northwest of its intersection with SR 1557 (CASWE-001). Muscovite mica also occurs in a pegmatite on the east side of SR 1559, 0.4 mile southeast of Semora (CASWE-OO2).
Cleveland County Muscovite occurs with spodumene at the Foote Mineral Company mine (inactive/closed) near Kings Mountain (CLEVE-013).
Harnett County Muscovite occurs in schists and gneisses small pegmatites with several other mineral at Raven Rock on the west bank of the Cape Fear River (HARNE-002). Raven Rock is part of the North Carolina Park System which prohibits the collecting of minerals and biological specimens.
Henderson County Rare-earth pegmatites occur in the area around Tuxedo and contain a wide of variety of minerals besides muscovite (HENDE-001, HENDE-002, HENDE-003).
Jackson County Muscovite occurs in pegmatites southeast of Pinhook Gap (JACKS-010) and at the Sheepcliff mine 3 miles north of Cashiers (JACKS-002).
Lincoln County Muscovite, tourmaline, smoky quartz and biotite occur as float in a field, 0.6 mile west of Flay (LINCO-001).
Mitchell County The Spruce Mine Mining District is one of the chief mica- and feldspar-producing areas in the United States.

Feldspar, plagioclase, quartz and mica (muscovite) occurs at the McKinney mine (fee charged) (MITCH-015). Other accessory minerals that occur are samarskite, garnet, autunite, torbernite, columbite, hyalite, amazonite, bornite, covellite, chalcopyrite, allanite, epidote, malachite, sphalerite and massive beryl. To get to the mine take Highway 19-E west from Estatoe, at 1.3 miles turn left (south) on SR 1002, at approximately 4.8 miles turn on to SR 1100. The mine is on both sides of the road (now Emerald Village and the North Carolina Mining Museum).

Feldspar, plagioclase, perthite, quartz and muscovite mica can be found at the Hootowl mine (abandoned) (MITCH-017). This mine can be reached by taking Highway 19-E west from Estatoe, at 0.37 mile turn left (south) on SR 1157, at 0.4 mile take the right fork, at approximately 0.9 mile the state road ends and a private road begins. The mine is on the left (east) side of the road. The Hootowl is shown and labeled on the Micaville 7.5 minute topographic map.

Feldspar, plagioclase, quartz and muscovite mica along with accessory minerals biotite, garnet and tourmaline (rare) are reported from the Sinkhole mine (abandoned) (MITCH-016). This mine can be reached by going 1.6 miles northwest from the intersection of SR 1191 and NC Highway 226 on SR 1191, turn left on Highway 80, at 2.3 miles the mine is to the left just before SR 1182. This mine is shown on the Micaville 7.5 minute topographic map.

Another collecting locale is at the Deer Park mine (abandoned) (MITCH-008) northwest of Spruce Pine. Feldspar, perthite, plagioclase, quartz and mica can be found with accessory minerals thulite, hyalite and monazite. At the intersection of NC Highway 226 and SR 1162, north of Spruce Pine, turn left (southwest) on to SR 1162 (Penland Road). Travel approximately 1.6 miles to Penland and cross bridge over the North Toe River. Turn immediately left (east) on to SR 1270 for a very short distance. After state maintained road ends continue on unmaintained 4-wheel drive road that parallels the river to the mine area in bend of the North Toe River approximately 0.7 of a mile. This mine is shown on the Spruce Pine 7.5 topographic map.
Swain County Muscovite occurs as an accessory mineral in the boitite-bearing pegmatites that occur in a northeast-southwest trending band north of Bryson City (SWAIN-002).
Wake County Muscovite occurs at the Nello Teer Crabtree Creek Quarry (active) (WAKE-011).
Yancey County Feldspar (plagioclase), perthite, quartz and muscovite occur at the Ray (Wray) mica mine (abandoned) (YANCE-001). Other minerals reported are golden and aquamarine beryl, apatite crystals, clear oligoclase (plagioclase feldspar), amazonite, thulite, garnet, autunite, columbite-tantalite, tourmaline, zircon and rutile. To reach this mine turn south on to NC Highway 197 from US Highway 19-E in Burnsville. Travel 0.9 mile to an intersection with SR 1109. Turn left (east) and travel along SR 1109 (Bowlens Creek Road) for approximately 1.4 miles to the intersection with SR 1192, nearly opposite the Bowlens Creek Church. Turn left (east) on to SR 1192 for about 0.3 mile where the state maintained road ends and a 4-wheel drive road leads to mine workings a little further ahead on left. This site lies in the Pisgah National Forest.

Biotite (black mica)
Chemical
Composition
K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2, Potassium magnesium, iron, aluminum silicate.
Class Silicate
Crystallography Monoclinic; prismatic
Habit CIn tabular or short prismatic crystals with prominent basal planes. Crystals rare,
frequently pseudorhombohedral. Often in disseminated scales.
Physical
properties
Cleavage {001} perfect. Plates flexible and elastic to brittle. H. 2.5-3.
S.G. 2.7-3.4. Luster splendent also vitreous. Color black; deep shades of brown, reddish
brown or green; more rarely light-yellow to white. Streak colorless. Transparent to
subtranslucent.

Map of Mica Mineral Localities

Mineral localities and descriptions of localities are from Wilson and McKenzie (1978) and Conley (1958). These locations have not been field checked for accuracy, minerals present or for accessibility. The site code (e.g. AVERY-002) refers to the site reference in the Mineral Locality Index.

Occurrences

Biotite is a common rock-forming mineral in the Blue Ridge and Piedmont provinces. It can be found in many igneous and metamorphic rocks and to a much lesser extent in the Coastal Plain sands as small flakes. It is more noteable when it occurs in pegmatites where it can be very large in size.

Ashe County The Duncan mine (abandoned), 1.2 miles southwest of West Jefferson was worked for mica and it also contains beryl (ASHE-001).
Cleveland County Biotite occurs with spodumene at the Foote Mineral Company mine (inactive/closed) near Kings Mountain (CLEVE-013).
Harnett County Biotite occurs in schists and gneisses small pegmatites with several other mineral at Raven Rock on the west bank of the Cape Fear River (HARNE-002). Raven Rock is part of the North Carolina Park System which prohibits the collecting of minerals and biological specimens.
Jackson County Biotite occurs in pegmatites southeast of Pinhook Gap (JACKS-010).
Lincoln County Biotite, tourmaline, smoky quartz and muscovite occur as float in a field, 0.6 mile west of Flay (LINCO-001).
Macon County Associated with garnet on Masoní Mountain, 1.6 miles east-southeast of Wests Mills and 1 mile south of Cowee Creek (MACON-002).
Mitchell County Biotite may occur as an accessory mineral in some of the mines and prospects of the Spruce Pine Mining District. See muscovite occurrences for Mitchell County collecting sites.
Swain County Biotite bearing pegmatites occur in a northeast-southwest trending band north of Bryson City (SWAIN-001, SWAIN-002).
Yancey County Biotite may occur as an accessory mineral in some of the mines and prospects of the Spruce Pine Mining District. See muscovite occurrences for a Yancey County collecting site.

Lepidolite (pink mica)
Chemical
Composition
K2Li3Al4Si7O21(OH,F)3, Potassium, lithium, aluminum fluorosilicate.
Class Silicate
Crystallography Monoclinic; prismatic
Habit Crystals usually in small plates or prisms with hexagonal outline. Commonly in
coarse- to fine-grained scaly aggregates.
Physical
properties
CCleavage {001} perfect. H. 2.5-4. G. 2.8-3.0. Luster pearly. Color pink and
lilac to grayish white. Translucent.

Map of Mica Mineral Localities

Mineral localities and descriptions of localities are from Wilson and McKenzie (1978) and Conley (1958). These locations have not been field checked for accuracy, minerals present or for accessibility. The site code (e.g. AVERY-002) refers to the site reference in the Mineral Locality Index.

Occurrences

Lepidolite is a rare mineral sometimes found in pegmatite rocks.

Granville County Lepidolite occurs as float in a field 2 miles north of Pocomoke on the Granville-Franklin County line (GRANV-006).
Warren County With smoky quartz and amethyst approximately 2.5 miles southeast of Inez (WARRE-001).

Margarite (brittle mica)
Chemical
Composition
CaAl4Si2O10(OH)2, Hydrous calcium aluminum silicate
Class Silicate
Crystallography Monoclinic; prismatic
Habit Seldom in distinct crystals. Usually in foliated aggregates.
Physical
properties
Cleavage {001} perfect. H. 3.5-5. S.G. 3.0-3.1. Luster pearly. Color grayish-pink,
pink, pale yellow, pale green. Streak colorless. Translucent. Folia somewhat brittle.

Map of Mica Mineral Localities

Mineral localities and descriptions of localities are from Wilson and McKenzie (1978) and Conley (1958). These locations have not been field checked for accuracy, minerals present or for accessibility. The site code (e.g. AVERY-002) refers to the site reference in the Mineral Locality Index.

Occurrences

Margarite occurs usually with corundum and apparently is one of its alteration products. Rare.

Iredell County At the Belts Bridge corundum occurrence on the south bank of the South Yadkin River 4.8 miles south of Harmony and 2.8 miles southeast of Turnersburg encasing some gray corundum crystals (IREDE-004).

Further Reading

The text was developed using the following references. See these for further information.

Ballew (1992)

Carr et al., eds. (1994)

Cook (1978)

Dana (1952)

Lesure (1968)

Hedrick (1996, 1997)

Paris (1994)

Reid, Carpenter and Davis (1998)

Stuckey (1953)

Wiener and Merschat (1977)

Wilson and McKenzie (1978)


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