538 Ci ELRDE, 
predominating. The upper division is also composed of conglomerate 
and slate, but the slate is comparatively unimportant. 
King’ describes the geology of the “Crystalline Belt” of Georgia, 
in connection with the occurrence of corundum. ‘The Crystalline 
Belt occupies an area of 12,430 square miles, crossing the northern 
part of Georgia from the northeast to the southwest, and lying between 
Paleozoic strata in the northwest corner of the state, and Mesozoic and 
Cenozoic strata in the southern half of the state. 
The rocks of the Crystalline Belt are divisable into two petro- 
graphical classes. ‘lhe first consists of a series of mica-schists, slates, 
shales, conglomerate, and marble, which, though more or less crystal- 
line, show evidence of clastic character. This class is called the semz- 
crystalline series. ‘The semicrystalline rocks are confined to an area 
bordering the Paleozoic to the northwest. The second class comprises 
eight types of rock. Three of them, limestone, quartzite, and slate, 
are undoubtedly clastic; three of them, granite, gneiss, and mica- 
schist, are completely crystalline and show no trace of clastic character ; 
and two, peridotite, and diorite, are presumably of eruptive origin. 
Gneiss and mica-schist are the prevailing rocks. This second class is 
termed the holocrystalline series. 
The rocks of the Crystalline Belt are separated from the Paleozoics 
on the northwest by a strong unconformity. Between the semi- 
crystalline and holocrystalline rocks there is apparent transition. 
Throughout the Crystalline Belt there is a uniform dip to the 
southeast, pointing toward a moving force from the southeast, but in 
the holo-crystalline area the dip is much steeper than in the semi- 
crystalline area. Disturbances and alterations are more extensive in 
the holocrystalline rocks than in the semicrystalline rocks. Corun- 
dum is present only in the holocrystalline rocks. 
From these facts it is believed that the holocrystalline area is 
older than the semicrystalline area, and formed the continent against 
which washed the waters of the sea which deposited the rocks of the 
semicrystalline series. While a portion of the holocrystalline series 
may be Archean, because of the presence in it of undoubted clastics 
the series is referred to the Algonkian. The same reference is made 
for the semicrystalline rocks. | 
*Corundum deposits of Georgia, Chap. iv, Geology of the Crystalline Belt, by 
Francis P. Ktnc: Bull. Geol. Surv. of Georgia, No. 2, 1894, pp. 58-72. 
