WHITLOCK. 



CRYSTAL FORMS OF CALCTTE. 



349 



a well marked zone containing several important forms. Palache 151 

 also observed this form on several crystals from the Lake Superior 

 region, on one of which the above mentioned zone is quite strongly 

 emphasized. The form also lies in zones [0443 : 2021] and [0554: 

 4041]. It should be classed as well established. 



b (4 -36 -40 -31) = (25- 21-15). This scalenohedron was also ob- 

 served by Palache on the same combination noted above, also 

 falling in the zone [0887 : 6281]. The form also falls at the intersection 

 of the zones [4047 : 0332] and [lOTl : 0443]. The form should be 

 classed as probable. 



R (8 -32 -40 -21) = (23- 15-17). This scalenohedron was noted by 

 Sansoni 152 on one crystal from Andreasberg. The combination figured 

 by Sansoni does not suggest any zonal relations between this scaleno- 

 hedron and the other forms present on the combination, nor does the 

 form lie in any well marked zone. On the other hand the hypothetical 

 scalenohedron (4 -15 -19-10) = (11-7-8), the pole of which lies very 

 close to (8-32-40-21) marks the intersection of several well defined 

 zones, viz: [011~2 : 1341], [0221 : 4153], [0772 :41o6] and [6174 : 3151]. 

 The agreement between the calculated angles of the hypothetical form 

 and Sansoni's measurements is shown below: 



1010 

 0110 



0887 

 1011 



hkil 



From the above table it would appear that in 3 out of the 4 angles 

 measured the form (4- 15- 19- 10) agrees with the measured angles 

 within the limits of fair observation and in one angle (4-15-19-10) 

 is closer to the observed value than (8-32-40-21). The form should 

 be classed as doubtful. 



C (1 • 13-14- 10) = (25-22-17). This scalenohedron was observed 

 by Whitlock 153 on crystals from West Paterson, N. J. In spite of the 

 fact that the Miller indices for this form are somewhat irrational the 

 zonal relations between this scalenohedron and other forms present 



151 Palache, C, loc. cit., Fig. 12. 



152 Sansoni, F., Atti. d. Lincei. Mem., 14, Fig. 8 (1884). 



153 Whitlock, H. P., Am. Jour. Sci., 24, 426 (1907). 



