THE 
AMERICAN GEOLOGIST. 
Vol. XXVII. APRIL, 1901. No. 4. 
THE GRANITIC ROCKS OF GEORGIA AND THEIR 
RELATIONSHIPS.* 
By Thomas Leonard Watson, Geol. Surv. of Georgia, Atlanta, Ga. 
PLATES XVII-XXIV. 
TABLE OF CONTENTS. 
Page. 
Introduction 199 
(a) The Even-Grained Normal Massive Granites 201 
Petrography 201 
The Oglesby-Lexington blue-gray granite 202 
The Elberton-Echol's Mill light-gray granite 203 
The Canipbell-Coweta-Mcriwether Counties' medium blue-gray 
granite 204 
The Stone Mountain light-gray granite 206 
(b) The Porphyritic Granites.. 208 
General description 208 
Petrography.. 208 
(c) The Granite-Gneisses 210 
The Lithonia belt of contorted gneiss 211 
Intrusive nature of the granites 213 
(1) Field relations 213 
Stratigraphic features 213 
Contact phenomena 214 
Basic inclusions 213 
Pegmatitic dikes 215 
(2) Chemical composition 216 
Table of cheiuical analj'ses 216 
Molecular ratios of the oxides 217 
(3) Mineral composition 219 
Microcline 220 
Muscovite 220 
Weathering 221 
Resume 222 
Structural features 222 
Age relations of the Georgia granitic rocks 223 
INTRODUCTION. 
In the present paper it is proposed to give a summary of the 
results obtained from several years' careful field and laboratory 
study of the granitic rocks, comprised within the limits of th(; 
Piedmont Plateau region of Georgia. 
"Published by permission of the State Geologist of Georgia. The writer 
wishes to acknowledge his indebtedness to Prof .James F. Kemp, of Columbia 
University, for kindly reading and criticizing this paper in manuscript. 
