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

More documents

Recommendations

Info

GEOLOGY OF THE DEPOSITS TABLE 1. Major deposits of Al2Si0 5 minerals Continued Kyanite Sillimanite Andalusite Deposits in micaceous schists and gneisses in the United States Dutchess County, N.Y. Burnsville-Swannanoa district, North Carolina Habersham and Rabun Counties, Ga. Blue Ridge area, Georgia Iron County, Wis. Boehls Butte quadrangle, Idaho Mount Monadnock, N.H. Dutchess County, N.Y. Southern Piedmont belt, North Carolina-South Carolina-Georgia Warne-Sylva belt, North Carolina Central Colorado (especially Holy Cross quadrangle) Southern Black Hills, S.D. Dillon, Mont. Troy, Idaho Boehls Butte quadrangle, Idaho Littleton, Mass. Boehls Butte quadrangle, Idaho Piscataquis County, Maine Deposits of much less importance are the pegmatites and quartz veins that contain kyanite, sillimanite, and andalusite, which are common in some areas of micaceous schist and gneiss in the South [Explanation of symbols: A, abundant (>10 percent) in all, or east. These deposits are small and are more noted most deposits, a, abundant (>10 as sources of fine mineral specimens than as minable percent) in only one, or a few deposits. ore deposits. C, common (1 to 10 percent) in all, or Kyanite, sillimanite, and andalusite are very re most deposits. sistant minerals; however, they may be liberated from the containing rock through weathering and become concentrated in some abundance in the soil. Minerals They are heavier than quartz, and accumulate along with the other heavy minerals in stream and beach placers. A few deposits of this nature are found in the region. Quartz........................... A DEPOSITS IN QUABTZOSE BOCKS TABLE 2. Relative abundance of minerals in quartzose deposits of Al 2SiOs minerals in the Southeastern States Aluminous minerals: Andalusite.................... Corundum Diaspore. . c, common (1 to 10 percent) in only one, or a few deposits. P, present (0.1 to 1 percent) in all, or most deposits. p, present (0.1 to 1 percent) in only one, or a few deposits. Kyanite- Kyanitequartquartz Sillimanite- Andalu- site-pyro- deposits, foliated variety1 deposits, nonfoliated variety2 quartz deposits 3 phyllite- quartz deposits4 Hypogene minerals The quartzose deposits of kyanite, sillimanite, and fyVophyiiite A andalusite seem to be more varied and more nu- itawoute6 . merous in the Southeast than in other parts of the ToSrmaiinV.'.'. '.'.'.'.'.'.'.'.'.'.'.'.'.'.'" Zunyite. ................... country. The following classes of the quartzose Clay minerals: group of deposits are found in the region: D?cidtetified clay mineral Kaolinite............... Kyanite-quartz deposits: _ Micas: Foliated variety White mica, unanalyzed.... C . T . . White mica, variety de- Nonfoliated Variety termined by analysis: Margarite. ............ p Sillimanite-quartz deposits Muscovite............. c i IT, , , ., Andalusite-pyrophylhte-quartz deposits Paragonite. ........... p Phosphates: The different classes of deposits are similar in chemical composition, consisting principally of Si0 2 vanscite and A120 3 , but are somewhat different in their mineral content and other geologic features. The other minerals: Apatite..... Bante........................ s mineralogic and geologic characteristics of each class p^lt of quartzose deposits are described below. The secular hematite' n ., , Sphalerite. major deposits and mineralogy of each class are sPhene......... Spinel.......... summarized in table 2. zircon........................ s p S, scarce (
8 KYANITE, SILLIMANITE, AND ANDALUSITE DEPOSITS, SOUTHEASTERN UNITED STATES TABLE 2. Relative abundance of minerals in quartzose deposits of AlaSiOs minerals in the Southeastern States Continued Minerals Kyanitequartz deposits, foliated variety1 Supergene minerals c Kyanitequartz deposits, nonfoliated variety2 Sillimanitequartz deposits3 s Andalusite-pyrophyllitequartz deposits* 1 Farmville district and Halifax County, Va.; Kings Mountain district, North Carolina-South Carolina (except Clubb Mountain); Youngs Mountain, N.C. ; Worth and Little Mountains, S.C. 2 Hagers Mountain, Corbett deposit, and Clubb Mountain, N.C.; Graves Mountain, Ga. 3 Reese Mountain, Machpelah Church, and Will Knox property, North Carolina ; Ryan-Purcley property, South Carolina. 4 Bowlings Mountain, Hillsboro, Snow Camp, and Staley, N.C.; Boles Mountain and Brewer topaz mine, South Carolina. KYANITE-QTJABTZ DEPOSITS Kyanite-quartz deposits are the largest and most numerous of the group of high-alumina quartzose deposits in the Southeast; their distribution is shown on plate 1. The principal minerals are kyanite and quartz, which together generally make up at least 90 percent of the rock. Several percent of muscovite or other white mica is present in most deposits. Pyrite is a common mineral in many deposits as small grains disseminated through the rock; limonite occurs in such deposits as a weathering product of pyrite. Rutile is a widespread but minor constituent, generally being present in amounts ranging between 0.5 and 1 percent; it occurs as minute grains included in quartz and kyanite. Less common minerals are pyrophyllite, lazulite, topaz, and various minor accessories including several aluminum phosphates and clay minerals (table 2). Two distinct varieties of kyanite-quartz rock foliated and nonfoliated r>?e found in the region. All foliated deposits are elongated parallel to the foliation of the enclosing rock; some nonfoliated deposits are discordant to the foliation. Some deposits consist of a single lens or layer; others are composed of a group of lenticular bodies arranged in echelon. Individual bodies range in width from a few feet to several hundred feet and in length from less than a hundred feet to several miles. The most persistent and largest deposits are in the Farmville district, Virginia, and the Kings Mountain district, North Carolina-South Carolina. The deposits in these districts exhibit many characteristics of folded and metamorphosed sedimentary rocks. On the other hand, the kyanite-quartz deposits at Graves Mountain, Ga., and the Corbett property, North Carolina, have certain features suggestive of replacement deposits. Kyanite-quartz rock is extremely resistant to weathering and erosion because of the relative insolubility of kyanite and quartz. The deposits characteristically form knobs or ridges; kyanite-quartz rock is well exposed in bold crags and cliffs in the largest deposits and in low ledges in the smaller ones. Willis and Crowders Mountains, The Pinnacle, and Graves Mountain are prominent monadnocks that rise several hundred feet above the general level of the surrounding country. The surfaces of the exposures of kyanite-quartz rock are generally very rough and jagged, because the quartz grains are eroded more rapidly than the kyanite crystals, which remain as rough projections. In contrast, barren quartzose rock weathers to smooth rounded surfaces. Thus, the degree of roughness of the weathered surfaces in many deposits is an index of the kyanite content. The surfaces of some exposures of kyanite-quartz rock are marked with pits, furrows, and irregular cavities resulting from the differential erosion of kyanite and quartz. Many cavities open downward and appear to have been developed and enlarged by the loosening and dropping out of grains of kyanite and quartz along small folds, foliation, bedding, and joint planes. PETROGRAPHY AND CHEMISTRY The kyanite-quartz rock commonly contains at least 90 percent combined A1203 and Si02 . Chemical and spectrochemical analyses of kyanite quartzite 1 from the Farmville district, Virginia, and the Kings Mountain district, North Carolina-South Carolina, are given in table 3. Quartz is the most abundant mineral in the kyanite-quartz deposits, generally making up 60 to 80 percent of the rock. In the nonfoliated varieties, quartz is typically very fine grained and forms a mosaic texture of unstrained grains (fig. 1). Quartz in foliated kyanite-quartz rock may be fine grained (fig. 2) or coarsely crystalline and strained (fig. 3). Kyanite generally constitutes 10 to 30 percent of the rock. It is most commonly white to light gray but is blue in several deposits. The mineral occurs in a wide variety of ways. In strongly foliated kyanite-quartz rock, the kyanite crystals are commonly segregated in layers of parallel crystals that are a centimeter or so long. Quartz inclusions may be present in kyanite in the fine-grained rock (fig. 2) 1 The terms "kyanite quartzite" and "sillimanite quartzite" are used in this report only for metamorphic rocks that probably were argillaceous sandstones originally. "Kyanite-quartz rock" is the name applied to metamorphic rocks that are either of probable nonsedimentary origin or of unknown origin ; it is also used as a general term for all rocks composed principally of these two minerals.
Page 1 and 2: Kyanite, Sillimanite, and Andalusit
Page 3 and 4: UNITED STATES DEPARTMENT OF THE INT
Page 5 and 6: IV Page Kyanite deposits Continued
Page 7 and 8: VI CONTENTS TABLES TABLE 1. Major d
Page 9 and 10: KYANITE, SILLIMANITE, AND ANDALUSIT
Page 11 and 12: KYANITE, SILLIMANITE, AND ANDALUSIT
Page 13: KYANITE, SILLIMANITE, AND ANDALUSIT
Page 17 and 18: Type of mica Muscovite . . . Do....
Page 19 and 20: 12 KYANITE, SILLIMANITE, AND ANDALU
Page 65 and 66:
58 KYANITE, SILLIMANITE, AND ANDALU
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
KYANITE, SILLIMANITE, AND ANDALUSIT
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
100 KYANITE, SILLIMANITE, AND ANDAL
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
120 KYANITE, SILLIMANITE. AND ANDAL
show all

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

Create successful ePaper yourself

Delete template?

Save as template?