46 The American Geologist. "^"'>'' ''^*'*- 
Analysis of Toxirmalinc. 
G. 2.991 
SiO. 35.57 
TiOa . 18 
B2O3 10.10 
AI2O3 24.72 
Fe^Os 1. 1 7 
FeO 9 . 40 
CaO 3.42 
MgO 8.29 
Na^O 2.10 
K.0 .40 
LhO 
H.0 4.23 
F. undet. 
99-58 
Biotite: Very common, usually in small plates dissem- 
inated throughout the rocks of the serpentme belt. Good 
crystals are occasionally found and one large on<^ in my 
possession measures 50 mm. in length. The smaller and 
more slender crystals are the most common . a_, silver-white ; 
h light brown ; c, dark brown . 
Analysis of Biotite. 
a b c 
G. 2.712 2.880 
Si02 41-07 41.12 40-32 
AI2O3 23.34 ^7-22> 18.03 
, K2O3 4-35 3-14 5-8o 
MgO 23.00 24.00 24.79 
CaO _ .89 .46 
NaiO 1.60' .42 
ICO 6.30 9.50 10.50 
H2O .26 3-56 .25 
99.92 99.86 100.15 
Prochlorite : Analyses of decomposed and altered olive- 
green {a) and light-green {^b) material from ^^'illiam'^ Bush- 
kill quarry afforded : 
a b 
G. 2.603 2.533 
SiO.. 33-96 34 01 
ALO.i 14-41 15-74 
FeO 3-8i 5-70 
CaO .12 . .14 
