Kyanite, Sillimanite, and Andalusite Deposits of the Southeastern ...

ECONOMIC CONSIDERATIONS 31
in 1939, and later worked a placer deposit on Raper
Creek. Mining ceased in the district in 1949.
Lump kyanite ore was shipped from Henry Knob,
York County, S.C., in 1935 and 1938 by B. J. Lachmond
(or Lockmund). In 1948, Commercialores,
Inc., began opencut mining- at Henry Knob, producing
kyanite concentrates by flotation; production has
been continuous since then.
In the 1920's and early 1930's small shipments of
lump kyanite gathered from pegmatites and quartz
veins in the Blue Ridge area of North Carolina and
Georgia were made by Philip S. Hoyt, and perhaps
others.
Complete production records for the kyanite
mines in the Southeast are not available. Since 1950,
all the production in the United States has come
from Baker and Willis Mountains, Va., and Henry
Knob, S.C.; in 1950 and 1951 it was estimated to
range between 16,000 and 20,000 tons of kyanite concentrates
annually (Watkins and Wolff, 1952, p. 10).
Production of crude kyanite increased annually from
1952 through 1955, according to the Minerals Yearbook
(U.S. Bur. Mines, 1952-1955). In 1954, kyanite
concentrates from the Baker Mountain mine
amounted to 15,608 tons (Corriveau, 1955, p. 4).
Kyanite is recovered from kyanite quartzite by
floation processes at those 3 mines. The concentrates
are sold as kyanite or mullite (calcined
kyanite) in various grain sizes: 35-, 48-, 100-, and
200-mesh.
The amount of sillimanite produced in the region
has been negligible. Stuckey (1937, p. 75) states
that in 1932 and 1933, Philip S. Hoyt shipped several
carloads of sillimanite from Clay County, N.C.
During the exploration of the Piedmont sillimanite
schist belt in Georgia, South Carolina, and North
Carolina in 1945 and subsequent years, large samples
of sillimanite schist were taken from different
localities for beneficiation and ceramic testing, but
no commercial shipments have been made. Highquality
refractory bricks were made from sillimanite
concentrates at the Bureau of Mines Electrotechnical
Laboratory, Norris, Tenn.
Andalusite has been produced only as a minor
constituent, not recognized until recently, in pyrophyllite
ores at several deposits in North Carolina;
it has not been separated from pyrophyllite by
milling processes. Massive topaz was produced from
the Brewer mine, Chesterfield County, S.C., from
1941 to 1948. The recorded production for 3 years
of this period amounts to 3,577 tons; the unrecorded
production was probably several thousand
tons.
ECONOMIC GEOLOGY
KYANITE DEPOSITS
Grade. Nearly all the kyanite produced in the
Southeastern States has come from deposits of kyanite-quartz
rock and kyanite schist or gneiss. The kyanite
content varies considerably from deposit to
deposit, but generally it is highest in kyanite-quartz
rock, commonly ranging between 20 and 30 percent
compared with a range of 5 to 15 percent in the better
deposits of kyanite schist or gneiss. The higher
grade of the quartzose deposits is doubtless one of the
reasons why mining has been continued at the quartzose
deposits of Henry Knob, S.C., and Baker and
Willis Mountains, Va., whereas mining of the deposits
of kyanite schist and gneiss of the Clarkesville district,
Georgia, and Celo Mountain, N.C., has ceased.
The kyanite schist in the Clarkesville district was
thought by R. W. Smith (1936) to have an average
of 6 to 8 percent kyanite in places favorable for
mining. Chute (1944,) states that the ore at Celo
Mountain was reported to carry between 10 and 11
percent kyanite at the beginning of operations, but
that in the latter half of 1943 the grade had declined
to between 7.0 and 7.5 percent. Kyanite content
of channel samples taken at Celo Mountain is
as much as 18 percent; about 55 percent of the
samples contained less than 10 percent kyanite (table
9). Kyanite in the ore mined at the quartzose
deposits of Baker Mountain and Henry Knob is
somewhat variable; the average grade of Baker
Mountain ore mined during the month of October
1954 was 15 percent kyanite, according to Corriveau
(1955, p. 2). Recent prospecting of the
quartzose deposit at Willis Mountain (22 miles
northeast of Baker Mountain) has shown that much
of that rock contains between 25 and 35 percent
kyanite (Jones and Eilertsen, 1954, p. 18-37).
The large kyanite crystals that are so common in
some quartz veins and pegmatites in areas of kyanite
schist in Georgia and western North Carolina
were encouraging to the prospecting of these deposits
at an early date; later it became evident that
such deposits were too small to be profitably mined
for kyanite. No reliable information is available on
their kyanite content; but it probably seldom exceeds
20 percent, and it may approximate the
average kyanite content of the country rock. Information
on the grade of kyanite in residual soil and
placer deposits is likewise very meager. Because of
its resistance to weathering, kyanite may accumulate
in considerable amounts in residual soils of
kyanite schist areas; locally, it may become concentrated
in more abundance in the soil than in the