Weathering of Diabase in Virginia. — Watson. 
95 
Table B shows the relationship existing between the 
partially and wholly decomposed rock. It is noteworthy, 
that a very much larger percentage of material has been dis- 
solved by dilute acid in the decomposed than in the partially 
altered rock. This is clearly the result of the oxidation of 
the ferrous to the ferric iron, and the retention of the oxidized 
product, since the iron has remained more nearly constant 
than any one of the other constituents. Of the individual con- 
stituents, 74.93 per cent of the silica, 70.42 per cent of the 
alumina, 98.75 per cent, of the lime, 98.28 per cent of the 
magnesia, 83.70 per cent of the soda, and 82.71 per cent of 
the potash have disappeared, equivalent to a loss of 69.53 P^^ 
cent for the entire rock. The calculations in tables B and C 
are made on a Fe^ Oa constant basis. Attention is here called 
to the unusually large percentage loss for the entire rock, which 
is rendered excessive by the very small amounts of silica and 
alumina retained. The loss in silica can be readily explained 
"C." 
Calculated Loss of Material in the Fresh and Decomposed Rock. 
Frosh 
Decomposed 
Calculated to 
Calcu 
lated amounts 
Olivine diabase 
Olivine 
Jiabase 
Total of iOO. 
saved and lost. 
I 
II 
III 
IV 
v 
VI 
VII 
VIII 
IX 
IS. 
.20 

«5 
2^3 
_>. 
ft-§ 
a-R 
l§ 
'" 


a 
a 
a 
'0'^ M 
to.2'^ 
a 
Sg 
a 
SCO 
a 3 
° a 
60S 
■^ 
■s o-c 
.X 
•5 cc 
a 
a a 
as 
a'^ 
M 
11 
fe 

© 
p 
H a 
SiO^... . 
45-73 
12.78 
37 09 
12.72 
45 -.38 
36-77 
33-41 
26.37 
73-64 
AlsO.,... 
13.48 
g. 10 
13-19 
8.22 
13-38 
13.08 
9. II 
31-81 
68.19 
♦FesO .. 
11.60 
8.7s 
35-69 
28.25 
II. 51 
35-39 
0.00 
100.00 
0.00 
CaO .... 
Q.92 
4-37 
0.41 
0.02 
9.84 
0.41 
9.71 
1.32 
98.68 
MgO. . . . 
15.40 
8.65 
0.57 
0.20 
15.28 
0.56 
15.09 
1. 19 
98.81 
NajO ... 
3-24 
Not del. 
1-75 
1. 00 
3.21 
1-73 
22.64 
17-54 
82.46 
K3O .... 
0.47 
" 
0-33 
0.20 
0.47 
0-33 
0.35 
22.69 
77-31 
H3O .... 
0.94 
0.94 
11.83 
11.83 
0.93 
"-73 
0.00 
100. oot 
0.00 
Total . . . 
100.78 
44-59 
100.86 
62.44 
100.00 
100.00 
170.31 
*Iron is taken as the constant factor in the above calculations. 
tGain. 
JPer cent. 
