Piedmont Plateau of Georgia. — Watson. 203. 
Chemical Analyses of the Oglesby-Lexington Dark Blue Granite. 
I 
II 
III 
IV 
V 
VI 
VII 
VIII 
Si02 
70.38 
70.30 
70.18 
70.03 
69.74 
69.64 
69.53 
69.36 
AI2O3* 
16.47 
16.17 
17.30 
15.62 
16.72 
17.21 
16.46 
17.23 
F'e203t 
1.17 
1.19 
1.20 
1.31 
1.45 
1.32 
1.15 
1.43 
CaO 
1.72 
2.61 
2.03 
2.45 
1.93 
2.14 
2.10 
2.14 
MgO 
0.31 
0.31 
0.64 
0.52 
0.36 
0.66 
0.85 
0.59 
K2O 
5.62 
4.88 
4.77 
5.42 
5.33 
4.95 
4.91 
4.57 
Na20 
4.98 
4.72 
4.36 
4.82 
4.84 
4.53 
5.00 
5.17 
Igni 
0.31 
100.96 
0.63 
0.35 
0.77 
0.47 
0.35 
0.91 
0.33 
Total 
100.81 
100.83 
100.94 
100.84 
100.80 
100.91 
100.82 
I. 
Biotite g 
jratiite from Swift & Et 
;heridge 
quarry, 
4 miles west of 
Elberton, Georgia. 
II. Biotite granite from Diamond Blue Granite Co.'s quarry, near 
Hutchins, Oglethorpe Co., Ga. 
III. Biotite granite from Brown & Deadwyler quarry, Madison coun- 
ty, Georgia. 
IV. Biotite granite from Lexington Blue Granite Co.'s Quarry, Lex- 
ington, Georgia. 
V. Biotite granite from Coggin's Granite Co.'s quarrj', near Ogles- 
by, Elbert county, Georgia. 
VI. Biotite granite from Coggin's Granite Co.'s quarry No. 2, near 
Oglesby, Georgia. 
VII. Biotite granite from outcrops near Hutchins, Oglethorpe county, 
Georgia. 
VIII. Biotite granite from the Child's quarry, near Oglesby, Georgia. 
The Elberton-Echol's Mill ^ght-Gray Granite: 
This type is represented by a belt ^i approximately the same 
dimensions and general direction aSf^the Oglesby-Lexington 
blue-gray granite, which it limits immediately on the southeast. 
The two areas are contiguous, and while w^ell differentiated as 
to color, and in a less degree texture, in their extreme portions 
they undoubtedly form parts of the same general area, as the 
gradation is well shown near Elberton and Carlton. 
The Elberton-Echol's Mill light-gray type does not differ 
essentially in mineralogy from the Oglesby-Lexington dark- 
blue granite, although they are strongly contrasted in the hand 
specimens. The difference is essentially one of color, with the 
biotite distributed at greater intervals and in somewhat stouter 
aggregated shreds in the light-gray granite. As a rule, the 
light-gray type is slightly more coarsely crystalline than the 
dark-blue variety. The same minerals are present in nearl}^ 
the same proportions and show the same characteristics in the 
two types. Quartz, orthoclase, microcline, plagioclase,' biotite, 
"Contains traces of P2O5, TiOz and ZtOz when present. 
fAll iron estimated as Fe203. 
