462 University Geological Survey of Kansas. 
There is an easy cleavage parallel to the prism faces of the 
second order, while cleavage is difficult parallel to the basal 
plane (pedion). 
The massive zinc sulphide upon which the wurtzite crystals 
are implanted usually assumes a botryoidal, mammillary or 
stalactitic form. It, too, is believed to be wurtzite. The 
color is dark brown, streak dark brown, and an optical ex- 
amination of its powder shows that some fragments are 
doubly refracting. Massive wurtzite can only be distin- 
cuished from massive sphalerite by optical means, and that 
even sometimes fails, as sphalerite occasionally exhibits 
anomalous double refraction. It seems probable, however, 
that our material is wurtzite, on account of its association 
and intimate connection with the wurtzite crystals. The 
crystals are formed directly out of the massive wurtzite, and 
there is perfect continuity between them and the latter. The 
color and appearance of the powder of the crystals and the 
massive mineral under the microscope are precisely the same. 
The powder of both the crystallized and massive wurtzite 
was compared with that of sphalerite, and the cleavage 
planes were found to be much fewer and less perfect than in 
the sphalerite. 
The only locality in the district for wurtzite is a deserted 
mine near the Missouri Pacific tracks, in the eastern part of 
Joplin, on the Missouri Lead and Zinc Company’s land. In- 
timately associated with it is galena in the peculiar reticulate 
or skeletal forms, as described under that mineral. 
An analysis of the massive zinc sulphide from this locality 
gave Mr. Edgar B. Hayes the following (the average of two 
analyses) : 
S51 Gas) SPR Mice pera Wear ee Co oa MLR .08 
| EY rarer aera Cees Ue PIE REN PD 2.46 
IP Denton ia eee aia care aga eae 7.24 
AURA ata he Pik eta Sammy yh.) 57.85 
hats aah a a a ree a SON 
98.70 
Calculating the Pb as PbS, deducting this and the SiO,, and 
recalculating to 100%, we have the following: 
1 Spa Sin Waals Hentai MB AME Ah ATS 
TAs Ae NaN REM RO UN A SON Ha eal 64.09 
SUR AUR Sts SOR UNM oat Ema IND tek 33.18 
