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Pyrophyllite Deposits in North Carolina," by Jasper L

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Pyrophyllite Deposits in North Carolina, Norih ouroiina Stare Library C/ Raleigh 3:80 North Carolina Q, 6.£ jyj e Doc. Department of Conservation and Development Dan E. Stewart, Director Division of Mineral Resources Stephen G. Conrad, State Geologist Bulletin 80 Pyrophyllite Deposits in North Carolina by Jasper L. Stuckey Raleigh 1967 Digitized by the Internet Archive in 2013 http://archive.org/details/pyrophyllitedepo1967stuc North Carolina Department of Conservation and Development Dan E. Stewart, Director Division of Mineral Resources Stephen G. Conrad, State Geologist Bulletin 80 Pyrophyllite Deposits in North Carolina by Jasper L. Stuckey Raleigh 1967 MEMBERS OF THE BOARD OF CONSERVATION AND DEVELOPMENT James W. York, Chairman Raleigh R. Patrick Spangler, First Vice Chairman Shelby William P. Saunders, Second Vice Chairman Southern Pines John M. Akers Gastonia John K. Barrow, Jr. Ahoskie J. 0. Bishop Rocky Mount David Blanton Marion Harry D. Blomberg Asheville Robert E . Bryan Goldsboro William B. Carter Washington Arthur G. Corpening, Jr. High Point Moncie L. Daniels, Jr. Manteo Koy E . Dawkins Monroe Dr. J. A. Gill Elizabeth City John Harden . Greensboro Gilliam K. Horton Wilmington Dr. Henry W. Jordan Cedar Falls Petro Kulynych Wilkesboro William H. Maynard Lenoir W. H. McDonald Tryon Jack Pait Lumberton John A. Parris, Jr. Sylva Oscar J. Sikes, Jr. Albemarle T. Max Watson Spindale 11 LETTER OF TRANSMITTAL Raleigh, North Carolina March 1, 1967 To His Excellency, HONORABLE DAN K. MOORE Governor of North Carolina Sir: I have the honor to submit herewith manuscript for publication as Bulletin 80, "Pyrophyllite Deposits in North Carolina," by Jasper L. Stuckey. This report contains detailed information on the occurrence, distri- bution and geology of pyrophyllite in North Carolina and should prove to be of considerable value to those interested in the mining and processing of this valuable mineral resource. Respectfully submitted, DAN E. STEWART Director m CONTENTS Page Abstract 1 Introduction 1 Previous work 1 Geology of the Carolina Slate belt 4 General statement 4 Distribution and character of the rocks 4 Felsic volcanic rocks 5 Mafic volcanic rocks 6 Bedded argillites (volcanic slate) 6 Igneous intrusive rocks 7 Environment of deposition 7 Structural features 7 Age of the rocks 8 Geology of the pyrophyllite deposits 9 Introduction 9 Distribution 10 Geologic relations 11 Form and structure 11 Mineralogy of the deposits 12 Pyrophyllite 12 Quartz 12 Sericite 12 Chloritoid 12 Pyrite 13 Chlorite 13 Feldspar 13 Iron oxides 13 High alumina minerals 13 Petrography 13 Origin of the pyrophyllite deposits 14 Earlier theories 14 Analyses of rocks 16 Origin of North Carolina pyrophyllite 18 Source of mineralizing solutions 18 Conditions of pyrophyllite formation 19 Reserves 19 Mining methods 20 Processing 21 Uses of pyrophyllite 21 Mines and prospects 23 Granville County 23 Daniels Mountain 23 Bowlings Mountain 23 IV Long Mountain 24 Robbins prospect No. 1 24 Jones prospect 24 R. E. Hilton property 24 E. C. Hilton property 24 Robins-Uzzell property 25 Robbins prospect No. 2 25 Orange County 25 Murray prospect 25 Hillsborough mine 25 Teer prospects 25 Alamance County 27 Snow Camp mine 27 Major Hill prospects • 27 Chatham County 28 Hinshaw prospect 28 Randolph County 28 Staley deposit 28 Pilot Mountain prospects 28 Moore County 29 McConnell prospect 29 Jackson prospect 30 Bates mine 30 Phillips mine 30 Womble mine . .31 Reaves mine 31 Jones prospect 33 Currie prospect 33 Ruff prospect 33 Hallison prospect 33 Standard Mineral Company 33 Tucker and Williams pits 35 Sanders prospect . .35 Montgomery County 36 Ammons mine 36 North State property 1 36 North State property 2 36 Cotton Stone Mountain 37 Standard Mineral Company 37 References cited 37 ILLUSTRATIONS Facing Page Plate 1. Pyrophyllite deposits in North Carolina 23 2. Piedmont Minerals Company 26 A. Mill B. Open pit mine 3. Glendon Pyrophyllite Company 32 A. Mill B. Open pit mine (Reaves) 4. Standard Mineral Company 34 A. Mill B. Open pit mine VI Pyrophyllite Deposits of North Carolina By Jasper L. Stuckey ABSTRACT All the known occurrences of pyrophyllite in North Carolina are found in Granville, Orange, Alamance, Chatham, Randolph, Moore and Montgomery counties where they are associated with vol- canic-sedimentary rocks of the Carolina Slate Belt. These rocks consist of lava flows interbedded with beds of ash, tuff, breccia and shale or slate that vary in composition from rhyolitic, or acid, to andesitic, or basic, and fall into three natural groups : Felsic Volcanics, Mafic Volcanics, and Bedded Argillites (Volcanic Slate). They have been folded, faulted and metamorphosed to the extent that they contain a well defined cleavage that strikes northeast and dips, in general, to the northwest. The pyrophyllite deposits which are irregular, oval or lens-like in form occur in acid volcanic rocks that vary from rhyolite to dacite in composition. The field, microscopic and chemical evidence indicates that the pyrophyllite bodies were formed by metasomatic replacement of the host rocks through the agency of hydrothermal solutions under conditions of intermediate temperature and pressure. Pyrophyllite has a variety of uses chief of which are in paints, rubber goods, roofing materials, ceramic products and insecticides. Reserves, while not large, are ample for several years. INTRODUCTION character and well developed cleavage, were called slates by a number of investigators over a The pyrophyllite deposits of North Carolina are period of 70 years before their true nature began associated with volcanic-sedimentary rocks of the to be recognized. The first published report on Carolina Slate Belt. Volcanic-sedimentary and that part of the slate belt in which pyrophyllite similar rocks form a belt or zone along the east- deposits are known to occur was a descriptive list ern border of the Piedmont Plateau and parts of rocks and minerals from North Carolina by of the Coastal Plain all the way from the vicinity Denison Olmsted (1822). In this list he de- of Petersburg and Farmville, Virginia, southwest scribed novaculite, slate, hornstone, whetstone across North Carolina, South Carolina and into and talc and soapstone from several counties in- Georgia, as far as the southern part of Baldwin cluding Orange and Chatham. He stated that the County south of Milledgeville—a total distance talc and soapstone were extensively used for of over 400 miles. In North Carolina the zone building and ornamental purposes and added that occupied by volcanic-sedimentary rocks is known Indian utensils of the same materials were com- as the Carolina Slate Belt. It is in this belt that mon. the pyrophyllite deposits of the state are found. In 1823, Olmsted was appointed by the Board The western border of the Carolina Slate Belt of Agriculture to make a geological survey of the lies a few miles east of Charlotte, Lexington and State. In his first report (1825) he called atten- Thomasville, crosses Guilford County southeast tion to the "Great Slate Formation which passes of Greensboro and continues northeast across the quite across the State from northeast to south- northwest corner of Alamance and Orange coun- west covering more or less of the counties of ties and the center of Person County to the Vir- Person, Orange, Chatham, Montgomery — ." The ginia line. The eastern limits of this belt are presence of talc and soapstone was noted in marked, by the cover of Coastal Plain sediments. Orange, Chatham and other counties together PREVIOUS WORK with beds of porphyry in the eastern part of the formation and bands of breccia consisting of rolled pebbles Due to the presence of a wide variety of min- interbedded in a ferruginous green- stone in erals in them, the rocks of the Carolina Slate different places. Belt have been of interest for approximately 150 Ebenezer Emmons (1856), one of the most years. These rocks, because of their complex competent geologists of his time, considered the Carolina Slate Belt rocks to be among the oldest cies." He classed the slate belt rocks as Precam- in the country and placed them in his Taconic brian in age. system which he divided into an upper and lower Nitze and Hanna (1896) first used the name member. The upper member consisted of clay Carolina Slate Belt for the rocks Olmsted (1825) slates, chloritic sandstones, cherty beds and brec- had designated the "Great Slate Formation." ciated conglomerate. The lbwer member consisted They recognized the occurrence of volcanic rocks of talcose slates, white and brown quartzites and in the slate belt and suggested that there had conglomerate. He did not recognize the presence been more than one volcanic outbreak and during of volcanic rocks in what is now known as the at least one period of inactivity slates had been Carolina Slate Belt. In his lower unit, Emmons deposited. They did not mention pyrophyllite but found what he considered to be fossils and named described in some detail the Bell, Burns and them Paleotrochis major and Paleotrochis minor. Cagle gold mines, all of which are in the pyro- Diller (1899) recognized these as spherulites in phyllite area along Deep River in Moore County rhyolite. and pointed out that there had been much silicifi- Emmons described in some detail the phyro- cation at all of these and some propylitic altera- phyllite deposits near Glendon, Moore County, tion at the Bell mine in particular. then known as Hancock's Mill and classed the Pratt (1900) described the pyrophyllite de- talcose slates, or those containing the pyrophyl- posits near Glendon and showed by chemical lite, as the basal member or oldest rocks of his analysis that the mineral is true pyrophyllite. He Taconic system. He further pointed out that pyro- described the pyrophyllite deposits as follows: phyllite occurred in the same position in Mont- "They are associated with the slates of this region gomery County. but are not in direct contact with them, being usually separated by bands of siliceous and iron Prior to this time the pyrophyllite had been breccia which are probably 100 to 150 feet thick.
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