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

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KYANITE DEPOSITS 87 EXPLANATION Metamorphic rocks are not necessarily, in strict stratigraphic order r /fe, ^.:.? kq? :;x:x¥/ k?| V^^ ^l^gp^/ ^^|$£$$\ ^5^^ ;^feSSS Chloritoid schist with some interlayers of white mica schist Contact Dashed where inferred -J.8 Strike and dip of foliation Strike and dip of foliation Probably slumped Strike of vertical foliation Direction and magnitude of plunge of axis of small fold ^S| >Sz:^Y-:.%WxV ^ Msfei Horizontal fold axis Vertical fold axis ^ vj"Y"."Y"YfeyYv-,v ^M^l^f/gl|ll' s ey^::\:;VlTO5jeeXv.^-^:||;«,/ Q N Direction and magnitude of plunge of kyanite blades Vertically plunging kyanite blades J37 Strike and dip of joints 91? Strike of vertical joints + Horizontal joints !tM&£6f$ m&W£g? ft -hi: :t * . .!< - .-- :-* N "^ i i i i i i i i i 200 400 I 600 I 800 Feet Plammetric base enlarged from aerial photograph Geology mapped by D.B. Potter, 1952 FIGURE 52. Geologic map of The Pinnacle, Gaston County, N.C.
KYANITE, SILLIMANITE, AND ANDALUSITE DEPOSITS, SOUTHEASTERN UNITED STATES Well-developed foliation (fig. 48) is parallel to bedding, and, in general, dips steeply and conforms to the shape of the quartzite outcrop. This is particularly true at the south end of the deposit. Small randomly oriented folds, with amplitude and wave length from 1 to 15 feet, are abundant throughout the kyanite quartzite of this deposit. The gently plunging and horizontal small fold axes in the high southern half of the mountain (fig. 52) suggest that the anticlinal axis there may be virtually horizontal. The northern half of the mountain, lying some 150 to 200 feet below the summit, is underlain by chloritoid schist which is surrounded by kyanite quartzite. In the northern half of the deposit, linear elements in kyanite quartzite plunge inward towards the enclosed chloritoid schist, suggesting that the quartzite beds converge at depth. Figure 52 shows that the kyanite content is highly variable throughout the deposit. The boundaries between quartzite containing 5 to 30 percent kyanite and quartzite containing 0 to 5 percent kyanite are not well defined. The largest concentration of kyanite is at the northeast end of the deposit where kyanite seems to constitute more than 20 percent of the rock. Kyanite quartzite at The Pinnacle contains abundant limonite. At some places limonite forms a hard outer rind which promotes cavernous weathering of softer rock beneath. Most of the limonite was derived from the weathering of small disseminated crystals of pyrite. Thin-section study of kyanite quartzite from this deposit indicates that kyanite occurs as subhedral to irregular anhedral crystals. Individual blades or grains of kyanite hold few quartz inclusions, but generally have irregular contacts with quartz; not uncommonly the kyanite blades are bent, fractured, and faulted. Some lenticular bands of coarsegrained quartz in the groundmass may represent highly flattened quartzite pebbles. Accessory minerals include white mica, pyrite, magnetite, rutile, zircon, and apatite. CHOWDERS MOUNTAIN Crowders Mountain, located in the northern part of the Crowders Mountain-Henry Knob area and about 4 miles east of the city of Kings Mountain, is a long high craggy ridge. The relief ranges from about 25 feet at the south end of the ridge where the kyanite quartzite outcrop is narrow (pi. 7; fig. 42) to about 750 feet at the middle of the ridge where the quartzite outcrop is widest. The shape of the ridge is accurately shown by the shape of the quartzite outcrop. The north nose of Crowders Mountain has a relief of about 550 feet. Sheer cliffs, 100 to 150 feet high, occur along the east and west side of the mountain north of the radio tower. Two principal types of quartzite are interlayered at Crowders Mountain, kyanite quartzite and massive ferruginous quartzite with generally only minor amounts of high-aluminous minerals. The individual outcrops have a northerly strike and very steep dip, and are intensely folded. The amplitude and wave length of these folds range from a few inches (fig. 47) to several hundred feet. In the southern half of the mountain the small fold axes and kyanite blades plunge consistently to the south; throughout the northern part most linear elements plunge to the south, but some plunge north and some are horizontal. As the overall structure of the quartzites in the vicinity of Crowders Mountain is not well known, two structural interpretations are given. Both interpretations assume that the thick quartzite outcrops mark the approximate position of the nose of the north-plunging South Fork anticline. Interpretation 1 (pi. 7) presupposes that the quartzite outcrops represent a single quartzite bed repeated by faulting and folding. These folds, steeply plunging anticlines and synclines with nearly vertical axial planes, were presumably superposed on the South Fork anticline. Brecciated schist, cemented with limonite, occurs at the north end of Crowders Mountain along the fault that borders the mountain on the east. Shear zones occur in the zone of dickite alteration on the east side of the mountain and along the fault one-quarter mile west of the radio tower. Interpretation 2 presupposes the presence of three quartzite beds at different stratigraphic positions (fig. 42). Bed A, the oldest, crops out at the Shelton property and along a low ridge southwest of the Lawton barite mine; bed B crops out about one-half mile west of the Shelton property and constitutes the main thick outcrops in the southern and central part of Crowders Mountain; bed C is represented by the long lenses of kyanite quartzite in the northern part of the mountain. Most of the quartzite exposed in the central and southern parts of Crowders Mountain is a massive gray ferruginous quartzite with little or no kyanite. Magnetite and staurolite are locally very abundant in this rock. Two thin sections of the staurolitic quartzite have the following estimated modal range:
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Kyanite, Sillimanite, and Andalusit
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UNITED STATES DEPARTMENT OF THE INT
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IV Page Kyanite deposits Continued
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VI CONTENTS TABLES TABLE 1. Major d
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KYANITE, SILLIMANITE, AND ANDALUSIT
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Type of mica Muscovite . . . Do....
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Kyanite, Sillimanite, and Andalusite Deposits of the Southeastern ...

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