I. M. Johnson mine

Mica Mine in Avery county, North Carolina

I. M. Johnson mine

Principal periods worked WWII
Workings 2 adits, 20 and 90, drift 45
Description of muscovite Green, minor ruby, "A" structure, bent, ruled, cracked, mineral inclusions.
Production Small sheet
Shape Tabular
Size 5-7 T
Strike NW
Dip SW
Relation to wallrock Concordance
Wallrock Interlayered hornblende and biotite gneiss
Extent of weathering Weathered
Remarks Pl-P-Q-M wall zone, medium grained; Q core.
Source of information USGS

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