SCHALLER.] 
DUMORTIERITE. 
107 
The mineral is orthorhombic, and from the various measurements 
the following axial elements have been calculated: 
a=.8897 
c=.6871 
The crystals were measured with the two-circle goniometer, and the 
values forj? and q 0> from which the above ratios are obtained, are 
#,=.7728 
?„=.6871 
The forms observed are as follows: 
I— Ooo —010 
a=ao = 100 
Z=oo2 = 120 
m=oo =110 
3 
n=2cc 
*=5° 
320 
210 
102 
203 
Besides these forms, reflections were obtained from several other 
minute faces, but they were so minute, and the reflections so poor, that 
their validity is very questionable and they are omitted from the fore- 
going list. The averages of the measured angles, compared with the 
calculated values, are shown in the following table: 
Letter and symbol. 
b =0x =010, 
a =co = 100 
I =oo 2 = 120 
m=cc =110 
(, =^co=320 
n =2oc =210 
d =|0 =102 
v =40 =203 
Measured. 
Calculated. 
*. 
o 
/ 

00 
111 
23 
29 
19 
49 
01 
59 
49 
65 
23 
91 
21 
87 
39 J 
90 00 
90 00 
90 00 
90 00 
90 00 
90 00 
46 
58 
00 
90 00 
29 20 
48 20 
59 19 
66 oi 
90 oo 
90 00 
90 00 
90 00 
90 00 
90 00 
90 00 
90 00 
21 
07 
14 
