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

50 KYANITE, SILLIMANITE, AND ANDALUSITE DEPOSITS, SOUTHEASTERN UNITED STATES
Tons per day
Percent kyanite
Mined _ _____.__ __ . ____..._ 550 15
Slimes to waste...__._. ____ 215 1
Feed to flotation............ ___.. 335 24
Flotation tailings ____ 250 4.4
Flotation concentrates _____ 85 82
Magnetic rejects ........... ____ 20 43
Final concentrate _..._..
65 94
Baker Mountain, a low rounded knob rising about
100 feet above the countryside, is capped by kyanite
quartzite which crops out in low massive ledges.
Although the overall dip of the kyanite quartzite is
at low angles to the south, the rock is highly deformed
by irregular minor folds whose plunges trend
in all directions. In places, layers of kyanite quartzite
a few feet thick have been compressed into
small recumbent folds or have been separated into
lenticular segments (boudinage structure) that are
surrounded by schist (fig. 29). Kyanite and muscovite
crystals are commonly in linear orientation.
The nature of the major structure at Baker Mountain
is by no means clear, but it is possible that
the broad curving belt of kyanite quartzite is on
the lower limb, or is the compressed crest, of a large
recumbent anticline. Features suggesting this structure
are the presence of only one belt of kyanite
quartzite (the crest of the fold?) to the east of
Baker Mountain and two belts of disconnected bodies
of kyanite quartzite (the limbs of the fold?) to the
west of Baker Mountain. At the west end of the
northern belt (about 800 feet west of the diabase
dike, pi. 3) small drag folds in the foliation of
kyanite quartzite consistently indicate the overturned
limb of an anticline.
Kyanite quartzite occurs on the property of James
Pugh near Madisonville, Charlotte County, about 3
miles west of Baker Mountain (pi. 3). The quartzite
is exposed in low ledges over widths as much as
40 feet. It appears to be in a very complex recumbent
fold that has intricate minor folds; the
general dip is to the east. The thickest and most
persistent belt of kyanite quartzite extends for
about half a mile northwest from Virginia Highway
47; it forms low, inconspicuous ridges in places.
Considerable exploration would need to be done to
determine the underground extent of the kyanite
quartzite, its thickness and grade, and the nature
of the rock lying between the layers of quartzite.
Thin ledges of kyanite quartzite in many outcrops
of variable orientation occur about li/2 miles north
of the Madisonville deposit, mostly east of Virginia
Highway 47; the irregularities of these outcrops are
probably due to folding.
The kyanite quartzite is typically a medium- to
coarse-grained gneissic rock that generally contains
a few percent of muscovite (figs. 3, 10); small
grains of rutile are a persistent minor accessory.
Much of the rock is heavily coated with limonite;
fresh rock usually contains several percent pyrite.
Some of the kyanite is white to light gray but
bright-blue kyanite crystals, an inch or more in
length, are found in parts of the Baker Mountain
deposit, near Madisonville, and at several other
places. A variety of green muscovite that occurs
with this blue kyanite at several places contains a
little chromium (table 4); kyanite is replaced by
green muscovite at a locality near Madisonville (fig.
10). A few percent of barite and spinel are present
in a thin layer of kyanite-quartz rock in the railroad
cut about 0.9 mile west of Baker Mountain mine;
kyanite occurs in small amounts in very garnetiferous
quartz rock about 0.2 mile east of the
latter locality.
The kyanite content of the kyanite quartzite of
this area varies considerably from place to place.
The amount of kyanite in composite grab samples
of kyanite quartzite taken from three localities has
been calculated from the partial chemical analyses
(table 8). It will be noted that the kyanite content
decreases progressively from east to west; this
change may be purely coincidental and have no
geologic significance. It is interesting that the
the amount of Ti02 (presumably all present as
rutile) varies directly with the A1203 content.
TABLE 8. Partial chemical analyses and calculated kyanite
content of kyanite quartzite from the Baker Mountain area*,
Prince Edward County, Va.
[Chemical analyses : W. J. Blake, Jr., analyst]
Kyanite quartzite samples
A1 20 3..........................
Fe 2O 3 (total) ...................
Ti0 2...........................
P 20 5......... ..................
VEP-71 VEP-72 VEP-73
23.82
.72
1.06
.02
Calculated kyanite content
Muscovite content 1 . .............
Kyanite content (calculated) ......
1.8
23.13
36.6
16.92
2.81
.62
.04
2.6
15.91
25.2
13.16
.69
.33
.03
2.0
12.37
19.5
1 Determined by heavy-mineral separation method.
2 Total AbOa theoretical amount of AhOs needed for muscovite.
Location of samples:
VPE-71, Lab. No. ID-5113. Composite of grab samples from crescentshaped
belt of kyanite quartzite, about half a mile east of Baker Mountain
mine.
VPE-72, Lab. No. ID-5114. Composite of grab samples from belt of
kyanite quartzite just west of Norfolk and Western Railway, about half
a mile west of Baker Mountain mine.
VPE-73, Lab. No. ID-5115. Composite of grab samples from scattered
outcrops of kyanite quartzite just east of Virginia Highway 47, about
2^4 miles west of Baker Mountain mine.