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

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KYANITE DEPOSITS 61 Kyanite schist and gneiss where mapped separately Border of mapped area The distribution of kyanite schist and gneiss north of 35°50' is generalized from geologic maps of the Spruce Pine district by D A Brobst, J L Kulp J C Olson, and others The general location of the belt of kyanite schist and gneiss south of 35°50' is described in the Mount Mitchell folio by Arthur Keith (1905) 5 Mile FIGURE 39. Map of kyanite schist and gneiss belt in Burnsville-Swannanoa area, North Carolina.
62 KYANITE, SILLIMANITE, AND ANDALUSITE DEPOSITS, SOUTHEASTERN UNITED STATES and 7.5 percent kyanite in comparison with an average of 10 to 11 percent kyanite in the early years of operation. The channel samples taken in the quarries by Chute, and from surface exposures by Mattson in 1929, provide excellent information about the distribution of kyanite in the gneiss here. These analyses are indicated on plate 6, and are summarized in table 9, which shows the distribution of samples in groups according to their kyanite content. TABLE 9. Distribution of kyanite in samples of kyanite gneiss from Yancey Cyanite Co. property Range in kyanite content (percent) 0- 3.9. .............. 4- 6.9. .............. 7- 9.9. .............. 10-12.9. .............. 13-17.9. .............. Percent of samples per grade group Chute's samples ' (106 total) 1.9 9.4 42.5 30.2 16.0 Mattson's samples (101 total) 13.9 21.8 17.8 29.7 16.8 1 The amount of kyanite in these samples was determined by heavy-mineral separation methods by R. L. Smith and Roswell Miller III, of the U.S. Geological Survey. The grade distribution of Chute's samples is not strictly comparable with that of Mattson's samples, because Chute's samples were not of uniform length (they ranged from 1.0 to 6.8 ft long), whereas Mattson's samples were all of the same length (2 ft). Nevertheless, it will be noted that in each group about 16 percent of the samples contain between 13 and 17.9 percent kyanite and about 30 percent contain between 10 and 12.9 percent. However, a much larger pecentage of Chute's samples (42.5 percent) falls into the 7- to 9.9-percent range than do Mattson's samples (17.8 percent). Probably one reason for the difference in this grade range is the fact that Chute's samples were all taken in the quarries, whereas 38 of Mattson's samples were taken from an exposure of lower grade kyanite gneiss to the west of quarry 1. The amount of garnet in Chute's samples does not range so widely as the kyanite. Garnet content in about 89 percent of the samples ranges from 7 to 12 percent, 6 whereas the kyanite content in about 89 percent of the samples ranges from 7 to 18 percent. Chute (1944) estimated the reserves of highgrade ore that might be mined by selective methods. Reserves were calculated for zones more than 6 Determined by R. L. Smith and Roswell Miller III. 10 feet thick that carried 12 percent kyanite or better. It was assumed that such ore could be projected 50 feet each way along the strike and 50 feet downdip; no allowance was made for pillars that might be left in underground mining. Five zones of kyanite gneiss that contained 106,474 tons of indicated ore having an average content of 12.5 percent kyanite were outlined. Very little of this ore was mined between the time of Chute's investigation in December 1943 and the shutdown of the mine in January 1944. Brobst (written communication, July 1953) has estimated that there are about 300 million tons of kyanite gneiss having an average content of 10 percent kyanite to a depth of 50 feet in the northern part of the Burnsville-Swannanoa district. The kyanite content may be less than 10 percent, however, to judge from the record of kyanite mining at Celo Mountain and the samples of kyanite gneiss from there (table 9). RUTHERFORD COUNTY Kyanite-quartz rock occurs southeast of Youngs Mountain, Rutherford County, in an area extending about half a mile east from the gravel road skirting the east side of the mountain. The locality lies about 5 miles northeast of the town of Lake Lure, and about 3 miles by gravel road north from U. S. Highways 64-74. The geology of about half a square mile in the vicinity of the deposits was mapped.(fig. 40) by P. K. Theobald, Jr., and J. W. Whitlow, of the Geological Survey. The principal rocks in the vicinity of the kyanite deposits are garnetiferous muscovite schist and biotite-quartz schist which contains few garnets. Biotite granite gneiss occurs here also, but is more widespread to the west where it underlies the main ridge of Youngs Mountain. Fine-grained hornblende gneiss is found in several small bodies in the kyanite area, and occurs in abundance to the north. Kyanite occurs as very fine grained white fibrous needles in coarse gneissic white quartz rock, accompanied by small shreds of muscovite and tiny rutile grains; the rock has a strong linear structure. The kyanite crystals are so fine grained and needlelike that they resemble sillimanite in the hand specimen, but microscopic examination shows that they are nearly all kyanite with only a very minor amount of sillimanite. The content of kyanite was about 29 percent in 1 thin section examined and 58 percent in another. Coarse blue bladed kyanite is also found in pegmatite lenses. The kyanite-bearing rock occurs mainly as float within the area
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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 Andalusite Deposits of the Southeastern ...

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