For the past three years the writer has been engaged in a careful detailed study of the granitic rocks of Georgia, giving special attention to the phenomena of their weathering. The natural outcrops have been carefully studied in the field, and specimens of the fresh and weathered rock, representing various stages in the decay, have been collected from the most typical and widely separated localities in the state and analyzed in the chemical laboratory of the State survey by the writer. The material is sufficiently representative and the work extensive and detailed enough to arrive at definite conclusions regarding the changes involved in the transition from fresh to decayed rock in the granitic group of rocks.
Based primarily on texture and structure, three types of the granitic rocks are distinguished: (1) The massive even-granular granites; (2) the porphyritic granites, and (3) the banded or foliated granites—gneisses. Laboratory study . . .