106 CONTRIBUTIONS TO MINERALOGY. [bull. 262. 
The accessories consist of pyrite, magnetite, possibly ilmenite, 
ieucoxene, and apatite. Considering the dumortierite as andalusite 
and calculating the soda in the analysis as potash, we get the following 
comparison: 
Calculated 
composition 
SiO, 
A1 2 3 
K,0 
H 2 
Accessories. 
57. 66 
33. 81 
3.19 
1.22 
4.12 
100.00 
Found. 
57. 18 
34.10 
3.16 
2. 02 
3.54 
100. 00 
It is interesting to compare the minerals from the three western 
occurrences, where feldspar is entirely absent, and the rock in each 
case is composed (essentially) of the following materials: 
Arizona : Dumortierite, quartz, muscovite, kyanite. 
California : Dumortierite, quartz, muscovite, sillimanite. 
Washington : Dumortierite, quartz, muscovite, andalusite. 
As the three minerals, kyanite, sillimanite, and andalusite have the 
same chemical composition, the composition of the entire rock is prob- 
ably also similar. 
CRYSTALLOGRAPHY. 
While the writer was at the California locality he made special 
search for crystals of dumortierite, but is forced to the conclusion 
that good, perfect crystals of the mineral are yet to be found. A 
large quantity of seemingly promising material was collected and 
afterward carefully examined with a lens. One minute crystal was 
found showing several fairly good faces in the prismatic zone and, 
when mounted on the goniometer, presenting minute terminal planes 
giving poor reflections. Further search afforded {mother crystal 
showing several prismatic faces but no terminations. 
The collection of specimens of dumortierite from Clip, Ariz., in the 
United States National Museum, was examined, and on one specimen 
was found a small crystal showing two prism faces and a dome. Fur- 
ther, three small crystals were obtained from the New York min- 
eral. On this poor material the following work is based. The results 
obtained are perhaps not accurate, but are the best that could be 
obtained. The California and New York crystals are long prismatic, 
while the Arizona crystal may be termed short prismatic. 
