SOME ADDITIONS TO THE ALUNITE-JAROSITE GROUP OF 
MINERALS. 
By W. F. Hillebrand and S. L. Penfield. 
Two new varieties of jarosite will be described in the present paper. 
One is from Nevada, and was collected by Mr. H. W. Turner, of 
the United States Geological Survey, and sent to the Survey labora- 
tory at Washington for identification; the other is from New Mexico, 
and was sent b}^ Mr. J. H. Porter, of Denver, Colo., to the min 
eralogical laboratory of the Sheffield Scientific School. Except fort 
slight differences in color the two minerals look exactly alike, eachii 
consisting of minute, isolated, tabular crys- 
tals, which, as may be seen with the micro- 
scope, are composed of combinations of at 
rhombohedron with largely developed basal I 
planes. By chance it happened that thai 
present writers discovered that they weraJ 
both engaged in the investigation of com- ] 
pounds belonging evidently to the same' 
group, and it was decided to bring thed 
results together into one paper. 
XATROJAROSITE. 
The material collected by Mr. Turner wasil 
obtained on the east side of Soda Springs ! 
Valley, Nevada, on the road from Sodaville 
to the Vulcan copper mine. It consists ol 
a glistening powder, made up of perfecl \ 
crystals having the habit shown in fig. 1, although generally only; 
one rhombohedron, /*, is present instead of two, as shown in the figure, j 
The largest crystals observed were 0.15 mm. wide and 0.025 mnxn 
thick, and the general average would not be over half that size. Ir 
spite of their minuteness, however, it was possible to measure the » 
angles of the crystals with the reflection goniometer, the chief dif j 
ficulty arising not so much from their small size as from the vicina j 
character of the basal planes. After repeated trials a crystal wat j 
32 
Fig. 1.— Natrojarosite. 
