FELDSPAR AND MICA DEPOSITS OF GEORGIA FRONTISPIECE CUT ON FLAT SHOALS ROAD NEAR SCHOOL HOUSE, LOT 110, 15th DJST., DeKALB COUNTY, GEORGIA, SHOWING PEGMATITE DIKE IN MICA SCHIS'.r. GEOLOGICAL SURVEY OF GEORGIA S. W. McCALLIE, State Geologist BULLETIN No. 30 A PRELIMINARY REPORT ON THE FELDSPAR AND MICA DEPOSITS OF GEORGIA BY !3. L. GALPIN, Ph. D., Assistant State Geologist ATLANTA, GA. CHARLES P. BYRD, STATE PRINTER 1915 THE ADVISORY BOARD OF THE Geological Survey of Georgia IN THE YEAR 1915 (Ex-Officio) HIS ExCELLENCY, JOHN M. SLATON ......... Governor of Georgia PRESIDENT OF 'I'HE BOARD HoN. PHILIP COOK .......................... Secretary of State HoN. W. J. SPEER .............................. State Treasurer HoN. W. A. WRIGHT ....................... Comptroller-Gene:·al HoN. WARREN GRICE ........................ Attorney-General HoN. J. D. PRICE ................... Commissioner of Agriculture HoN. M. L. BRITTAIN ............. Commissioner of Public Schools LETTER OF TRANSMITTAL GEOLOGICAL SuRVEY OF GEORGIA, ATLANTA, April 25, 1915. To His Excellency, JoHN M. SLATON, Governor and President of the Advisory Board of the Geological Survey of Georgia. SIR: I have the honor to transmit herewith the report of Dr. S. L. Galpin, Assistant State Geologist, on the Feldspar and Mica Deposits of Georgia, to be published as Bulletin No. 30 of this Survey. Very respectfully yours, S. W. McCALLIE, State Geologist. PREFACE The preparation of this report was authorized for the purpose of obtaining and supplying to the public, information regarding the occurrence and nature of the feldspar and mica deposits which exist in the State. That such information is in great demand is shown by the frequent inquiries concerning these minerals addressed to the Geological Survey. The report contains, in addition to descriptions of feldspar and mica deposits, one chapter dealing with the general geology of the .area in which these deposits occur, and a second detailing the nature of the rock pegmatite and the uses, values, and the like, of its most important minerals, particularly feldspar and mica. The collecting of this material was begun in May, 1912,. and con­ tinued until January, 1914. Much of the information was obtained .at first hand either in the field or from laboratory study. The re­ mainder has been collected from various sources which are indicated in the text by foot notes whenever possible to do so. Progress on the report was halted in January, 1914, by the writer's "Withdrawal from the active staff of the Survey. However, arrange­ ·ments were later perfected whereby he has been allowed to complete the work. He takes this opportunity to acknowledge the Survey's ·cordial co-operation, which has been a very material aid in the re­ -port's preparation. s. L. GALPIN. :Department of Mining and Geology, Iowa State College, Ames, Iowa. .. TABLE OF CONTENTS PAGE ADVISORY BoARD iii LETTER OF TRANSMITTAL •••.•.•................. iv PREFACE ••.•..•••••....•.•...•..•••.••.••••.... v TABLE OF CONTENTS .•.......•.......••.............................. vii-~~~ LIS'J' OF ILLUSTRATIONS xii PART I PAGE CHAPTER I. CRYSTALLINE AREA ..................................... 1·21 Geology ........................................................ 1 Location ....................................................... 1·2 Physiography ................................................... 2·5 Piedmont Plateau ............................................. 2·3 Appalachian Mountains • ........................................ 4-5 Weathering .................................................... 5·7 Structure ....................................................... 7-9 Geologic formations ............................................. 9-21 Petrographic groups .......................................... 9-11 Archean System .............................................. 11-21 Carolina gneiss ............................................. 11-12 Roan gneiss ................................................ 12-14 Cambrian sediments ........................................... 14-16 Early igneous rocks ........................................... 16-18 Early granites .............................................. 17-18 Gabbros, peridotites, etc ...................................... 18 Effusive rocks .............................................. 18 Later igneous rocks ........................................... 18-21 Later granites .............................................. 18-20 Injection gneisses and foliate granites .......................... 20-21 CHAPTER II. PEGMATITE .....••..................................... 22-50 Occurrence, composition, structure, etc ............................. 22-25 Origin of ....................................... ·............... 25-27 Useful minerals of .............................................. 27-50 Feldspar group ............................................... 27-39 Uses ...................................................... 30-31 Grading ................................................... 31-32 Impurities ................................................. 32-34 Testing .................................................... 34-35 Sampling .................................................. 35 Quarrying .................................................. 35-36 'l'reatment .......................................... · ·. · · · · · 36-37 vii PAGE Markets .......................................... · ... · · · · · · · 37 Production ................................................. 37-38 Value ...................................................... 38·39 Quartz ....................................................... 39·40 1\iica ................................................ ·........ 40·50 Uses ....................................................... 44-45 Grading .................................................... 45-46 Production ................................................. 46·47 Prices ............................ · ............... ·. · · · · · · · · · 47 Mining ..................................................... 47-48 Treatment ................................................. 48-50 PART II FELDSPAR AND MICA IN THE GEORGIA PEGMATI'rES ••••••..•.....••.....• 51 Introduction .................................................... 51·52 Section I, Baldwin, Hancock, McDuffie, Warren, Richmond and Columbia counties .................................................. 52·60 Topography .................................................. 52 General geology .............................................. 52-60 Carolina gneiss ............................................. 53-54 Roan gneiss ................................................ 54-55 Granites .................................................... 55-58 Pegmatites ................................................. 58-60 Baldwin County .......................................... 58·60 Warren County ........................................... 60 Columbia County .......................................... 60 Other counties ............................................ 60 Section II, Lincoln, Wilkes, Taliaferro, Greene, Putnam, Jasper an•l .Tones counties ............................................ 61·71 Topography and geology ....................................... 61·71 Carolina gneiss ............................................. 111·62 Roan gneiss ................................................ 62-\13 Granites· ...... : ............................................ 63-64 Injection gneiss ............................................. 64 Pegmatites ................................................. 64-71 Lincoln and Taliaferro counties ............................. 65 Wilkes County ............................................ 65 Greene County ............................................ 65-67 Putnam County ........................................... 67-68 Jasper County ............................................ 68 Jones County ............................................. 68-71 Section III, Butts, Monroe, Bibb, Crawford, Pike, Taylor, Harris, and Muscogee counties ..................................... 71-87 Topography and geology ....................................... 71-87 Carolina gneiss ............................................ · · 72-73 Roan gneiss ................................................ 73-74 viii PAGE The Pine Mountain formation ................................ 74-lli Granites IG-77 niorite ..................................................... 77 Injection gneiss ............................................ 77-78 Pcgmatites ................................................. 18-87 Butts County ............................................. 78 Monroe County ........................................... 79·8~ l\lica ................... · · . · · · · · · · · · · · · · · · · · · · · · · · 81·8~ Bibb County ................................ Cnnvfonl County ................................ 8~-SG .l\lica ..................................... S4 Taylor County ..................................... S.J rpson County ................................... s.:; Sli :\lica ................ ·. · · · · · · · s:J.:-,li Pike County ~(i Talbot County ............... ~ti-S/ ~Iica ........................... Si Harris County ..................................... ,~/ l\lica .............................................. ::""li :\luscogee County . Sl Section lV, Troup, Heard, i\lcri\Yethcr, CO\Yeta, Campbell, Fayette, Spalding, Clayton and Henry counties. SS-1 0 I Topography . ''S Geology . SS·l 01 Carolina gneiss ..................................