F. R. Van Horn — Pisanite and Arsenopyrite. 45 

 Fig. 3. Fig. 4. Fig. 5. 



771 



771 



777, 



771 



h 



Figs. 3, 4, and 5, Pisanite crystals from Isabella, Tennessee, drawn by Dr. 

 W. T. Schaller. 



Forms determined : 



b (010), very narrow, figs. 4 and 5. 



c (001), large figs. 3, 4, 5. Cleavage. 



m(110), large, dominant form, figs. 3, 4, 5. 



o (Oil), small, figs. 4 and 5. 



w (1<>3), minute, fig. 4. 



t (101), minute but larger than w figs. 3, 4, and 5. 



cr (121), minute, fig. 5. 



(Average) Measured and Calculated angles : 





Measured 



Calculated 





1> 



P 



<P 



P 



b (010) 



o°iV 



90° 00' 



0°00' 



90° 00' 



c (001) 



89 23 



15 54 



90 00 



15 11 



m (110) 



41 34 



90 00 



41 36 



90 00 



o (Oil) 



9 35 



57 19 



10 07 



57 04 



w (103) 



88 27 



36 29 



90 00 



35 48 



t (101) 



89 21 



47 06 



90 00 



47 09 



o- (121) 



18 33 



72 06 



19 32 



72 46 



The results of the crystallographic observations given above 

 prove conclusively that the blue mineral is pisanite and not a 

 mechanical mixture of melanterite and chalcanthite as some 

 might claim. 



Arsenopyrite. 



One of my students, Mr. P. A. Fruehauf, found in the schis- 

 tose walls of the ore body of the London mine, Ducktown 

 district, two crystals which he brought to the writer for deter- 



