Piedmont Plateau of Georgia. — Watson. 
217 
XVI 
XVII 
( 
XVIII 
jXEISSES 
XIX 
XX^ 
XXI 
XXII 
XXIII 
Meri-w'r Gwinnett Rockdale 
Heard : 
Lithonia 
Coweta 
Newton 
Clarke 
Cottnty 
County 
County 
County 
County 
County 
County 
Si02 
76.37 
75.86 
75.45 
74 96 
74.70 
73.95 
71.20 
69.51 
A1203' 
13.31 
14.02 
13.71 
13.71 
13.85 
14.23 
15.46 
16.32 
Fe203* 1.21 
0.71 
0.92 
0.90 
1.03 
1.29 
1.17 
2.38 
CaO 
1.13 
0.70 
0.94 
1.02 
1.08 
1.07 
1.36 
1.84 
MgO 
0.10 
0.12 
0.18 
0.2i 
0.17 
0.23 
0.38 
1.28 
K2O 
3.68 
5.56 
4.30 
4.79 
4.82 
5.29 
5.30 
3.47 
Na20 
4.02 
3.64 
3.87 
4.68 
3.94 
4.61 
4.96 
3.82 
Igni. 
0.20 
0.28 
0.40 
0.44 
0.28 
0.25 
0.52 
1.11 
Total 100.02 100.89 99.77 100.74 99.87 100.92 100.30 99.73 
Sp. Gr. 2.642 2.642 2.643 2.648 2.686 
B. MOLECULAR RATIOS OF THE OXIDES. 
Gr 
\NITES 
I 
11 
III 
IV 
V 
VI 
VII 
VIII 
Si02 
1.209 
1.165 
1.164 1.164 
1.159 
1.152 
1.149 
1.054 
AI2O3 
.145 
.156 
.160 
.164 
.163 
.160 
.164 
.195 
Fe203 
.005 
.007 
.012 
.008 
.006 
.008 
.007 
.017 
CaO 
.021 
.042 
.032 
.035 
.030 
.035 
.040 
.051 
MgO 
.005 
.014 
.009 
.012 
.006 
.011 
.022 
.012 
K2O 
.056 
.053 
.059 
.053 
.041 
.049 
.050 
.051 
NaaO 
.079 
.078 
.071 
.076 
.094 
.074 
.080 
.066 
K2O \ 
Na20 i 
.135 
.131 
.130 
.129 
.135 
.123 
.130 
.117 
PORPHYRITIC G 
RA.SITES 
IX 
X 
XI 
XII 
XIII 
XIV 
XV 
Si02 
1.181 
1.170 
1.162 
1.156 1 
.155 
1.152 
1.152 
AI2O3 
.155 
.164 
.167 
166 
.157 
.163 
.168 
Fe203 
.011 
.009 
.010 
012 
.011 
.007 
.009 
CaO 
.032 
.035 
.039 
036 
.040 
.036 
.033 
MgO 
.023 
.019 
.024 
021 
.009 
.015 
.019 
K2O 
.049 
.053 
.043 
048 
.048 
.047 
.058 
Na20 
.063 
■.059 
.064 
055 
.081 
.078 
.065 
K2O 1 
Na20 i 
.112 
.112 
.107 
103 
.129 
.125 
.123 
Granite-Gneisses 
XVI 
XVII XVIII XIX 
XX 
XXI 
XXII 
XIII 
Si02 
1.272 
1.264 
1.257 1.249 
1.245 
1.232 
1.186 
1.158 
AI2O3 
.130 
.137 
.134 
.134 
.134 
.139 
.151 
.160 
Fe203 
.007 
.004 
.005 
.005 
.006 
.008 
.007 
.014 
CaO 
.020 
.012 
.016 
.018 
.019 
.019 
.024 
.029 
MgO 
.002 
.003 
.004 
.006 
.004 
.005 
.008 
.010 
K2O 
.039 
.059 
.045 
.050 
.051 
.026 
.056 
.044 
Na20 
.064 
.058 
.062 
.075 
.063 
.074 
.080 
.070 
K2O 1 
Na20 / 
.103 
.117 
.107 
.125 
.114 
.110 
.136 
.114 
* All iron estimated as Fe203. 
° Average of 3 analyses representing different quarries. 
' Contains traces of P2O5, Ti02 and ZrOo when present. With sever- 
al exceptions, the usual qualitative test failed to indicate the presence 
of TiOa in the Georgia acid rocks. P2O5 and Zr02 are invariably present 
in small microscopic proportions as prismatic inclusions of apatite and 
Zircon. 
