30 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167 
Found. 
Reduced. 
Calculated. 
36.79 | 
P. and F. 
Rioga. 
P. and F. 
Riggs. 
Mean 
Si0 2 
36.72 
.05 
10.81 
29.68 
.22 
14.92 
3.49 
1.26 
.05 
2.98 
.93 
36.88 
.12 
10.58 
28.87 
.52 
14. 53 
3.70 
1.39 
.18 
3.56 
.50 
36.56 
36.81 
36.69 
Ti0 2 
B 2 3 
A1 2 ;! 
FeO 
MgO 
CaO 
Na.,0 
10.76 
29. 55 
J 14.97 
3.47 
| 1.28 
| 3.41 
10.56 
28.81 
14.79 
3.69 
1.50 
3.84 
10.66 
29.18 
14.88 
3. 58 
1.39 
3.62 
100. 00 
10.74 
29. 07 
14.86 1 
3.48 j 
1.44 
3.62 
K 2 
H 2 
F 
101. 11 
100. 83 
100. 00 
100. 00 
100. 00 
The dark brown tourmalines from Orford, New Hampshire, an( 
Monroe, Connecticut, as analyzed by Riggs, also reduced to simila 
form, and approximate to the mixture 
15. Al 5 (Si0 4 ) 6 (B0 2 ) 2 . B0 5 (A10H) . Mg 4 H 4 , 
6. Al 5 (Si0 4 )6(B0 3 ) 3 . BO ;i Ca . Mg 4 K 4 , 
8. Al 5 (Si0 4 ) 6 (B0 2 ) 2 . BO y NaH . Al 3 Na 2 H, 
with the comparison as follows: 
Found. 
Reduced. 
Calculated. 
Orford. 
Monroe. 
Orford. 
36.96 
10. 16 
i 33.28 
J 11.84 
1.36 
i 2.58 
3.82 
Monroe. 
Si0 2 
B 2 3 
A1 2 3 
TiO. 
36.66 
10.07 
32.84 
.23 
2.50 
10.35 
1.35 
2.42 
.22 
3.78 
36.41 
9.65 
31.27 
1.61 
3.80 
9.47 
.98 
2.68 
.21 
3.79 
37.34 
9.89 
33.13 
n.88 
1.00 
2.88 
3.88 
36.84 
10.74 
33.11 
11.85 
1.19 
2.62 
"3.65 
FeO 
MgO 
CaO 
Na,0 
K 2 
H 2 
100. 42 
99.87 
100. 00 | 100. 00 
100. 00 
Here the divergence between the composition as found and a 
calculated is evidently due to the low determinations of boric acid i 
the analyses. Still the comparison is close. 
