V202 



NEW YORK STATE MUSEUM 



gave goniometer readings which corresponded to the indexes (2-12) 

 and (3 13). The letters o^=:(2i2) and p-^(3i3) have been as- 

 signed to these forms. The distribution of the occurring forms 

 is as follows : 



LETTER 



SYMBOL 













CRYSTAL 















I 



II 



III 



IV 



V 



VI 



VII 



VIII 



IX 



X 



XI 



XII 



a 



100 



010 

 310 

 210 

 320 

 110 

 230 

 350 

 120 

 130 

 111 

 Til 

 212 

 313 



X 



X 



X 



X 

 X 

 X 

 X 









X 

 X 

 X 



X 







X 

 X 

 X 

 X 

 X 

 X 

 X 



X 

 X 



X 



b 



X 

 X 

 X 

 X 

 X 



X 

 X 

 X 

 X 

 X 



X 

 X 

 X 

 X 

 X 



X 

 X 

 X 



X 

 X 

 X 

 X 

 X 



X 



z 



T 



0. . . 



X 



X 





W 







f 



X 



X 



X 



X 



X 



X 



X 



2: 





d 









X 

 X 















h 



k 



X 



X 





X 

 X 

 X 

 X 

 X 

 X 



X 

 X 

 X 

 X 

 X 



X 

 X 

 X 

 X 



X 

 X 

 X 

 X 

 X 



X 



X 

 X 

 X 



X 



X 

 X 

 X 

 X 

 X 

 X 







1 



X 

 X 

 X 



X 



X 

 X 

 X 



X 

 X 



X 

 X 



X 

 X 



X 



n 







X 



P 



X 



X 



X 



X 



The following measured angles served to identify the forms ; the 

 theoretical angles are calculated from the elements given by 

 Beckenkamp^ and adopted by Goldschmidt in his KrystaUographische 

 Winkeltabellen. 



a:b:c = o.4i33:i 10.6895 ^ = 98° 58' 



Summary of measured and calculated angles 



, LETTER 



ANGLE 



NUMBER OF 

 READINGS 



MEASURED 



CALCULATED 



b :a 



b :z 



b. :«..... 

 b : r 



101 : 100 

 101 : 310 

 101 : 210 

 101 : 320 



5 

 10 

 17 



5 



, 



90 i 

 77 11 

 71 13 

 65 41 



/ 



90 

 77 12i 

 71 Hi 

 65 35 



' Zeitschr. f. Kryst. 1882. 6: 450. 



