schaller.] DUMORTIERITE. 105 
center, the ends .spreading- out into "brushes" of fine fibers. This 
form is fairly abundant, h forms a prismatic portion becoming fibrous 
at both ends, and while common in the New York, Arizona, and Cali- 
fornia occurrences, is a rare t}^pe for Washington dumortierite. c 
forms a sort of fan and is composed of several "brushes" joined to- 
gether. It is a common type, d is an elliptical spherulite. e is a 
mass of prisms such as />, but not spreading out as a does. It is of 
rarer occurrence, yis a hunch of radial fibers with no prismatic stem 
as in c. It is fairly common. 
To confirm the microscopical determination of the minerals of the 
rock a chemical analysis was made by the writer of a fresh sample of 
the rock. The results obtained are shown below. 
Si0 2 57. 18 
AM ) 3 , 34. 1 
Fe 2 O s 54 
FeO 28 
MgO 10 
CaO 63 
Na 2 39 
K 2 _-_' 2. 57 
H 2 0- 69 
H 2 0+ . . 2. 02 
Ti0 2 66 
Zr0 2 02 
C0 2 . - none 
P 2 5 53 
FeS 2 28 
MnO none 
BaO 04 
Sr< ) trace? 
LLC) none 
100. 03 
Out of 2«)(> grams of rock, 4.3 grams of dumortierite were obtained. 
Some was doubtless lost, and the sample still contained some andalu- 
site, but 2 to 2^ per cent would approximately represent the amount 
of dumortierite present. 
The mineralogical composition of the rock is about as follows: 
Andalusite 35 
Dumortierite 2 
Quartz 32 
Muscovite 27 
Acccsst >ries 4 
100 
