Big "A" mine

Mica Mine in Avery county, North Carolina

Big "A" mine

Principal periods worked Pre-1920, 1934, WWII, 1957.
Workings 6, adits, 5 cuts, extensive underground workings in area, 250 x 250 ft.
Description of muscovite Ruby and brown, clear, minor "A" structure.
Production Moderate sheet
Shape Lenses
Size 0-8 T
Strike NE
Dip Gentle NW
Relation to wallrock Partly concordant
Wallrock Interlayered hornblende and biotite gneiss
Extent of weathering Weathered (20 ft).
Remarks Pl-P-Q-M-B pegmatite, medium to coarse grained; accessory garnet, pyrite. Lenses are in zone 10-15 ft thick. Late faults cut pegmatite.
Source of information USGS, OF

Geographic context


Principal periods worked
WWI World War I
WWII World War II
int intermittent
Small < 500 lb
Moderate 500-10,000 lb
Large > 10,000 lb
Size of pegmatite
D depth
L length
T thickness
avg average
Internal structure
B biotite
F feldspar
M muscovite
P perthite
Pl plagioclase
Q quartz
Source information
CMC Colonial Mica Corporation
DMEA Defense Minerals Exploration Administration
OME Office of Minerals Exploration
USGS U.S. Geological Survey
OF USGS open-file reports and maps