280 C. ANDERSON. 



well developed but not so large as I (023), which is one of 

 the dominant forms; all three reflect well and give good 

 signals, although f, and particularly I, are sometimes 

 striated parallel to their intersections. None of the pyra- 

 mids are large; h (221), k (221), and R (241) are the best 

 developed and are invariably present. The rare pyramid 

 A (2*18*3), which is present on all but one of the crystals 

 with this habit, and always accompanied by the new form 

 X (481), is occasionally a fairly large polygonal face [Plate 

 V, fig. 4), separating iv and w, but usually it is quite small 

 and elongated. The following angular measurements were 

 obtained for A : 



Crystal. Signal. . cf> p 



2 



good 



7 6 



79 29 x 







4 



good 



7 7 



79 39 







5 

 5 



good 

 fair 



6 53 



7 3 



79 19 



79 27 



Average. 



Calculated 



5 

 5 

 5 

 6 



fair 

 fair 

 good 

 good 



6 55 

 6 42 



6 58 

 6 58 



79 25 

 79 25 

 79 23 

 79 32 



}<f> 6° 57 

 p 79 26 



6° 57 

 79 25 



6 



good 



6 53 



79 16 ) 



1 





Habit II [Plate VI] is characteristic of the crystals on 

 specimen 0. The crystals are, as before, elongated parallel 

 to the symmetry axis, but they have in this case a tendency 

 towards tabularity on the plane of the a and b axes, so that 

 the edge at the end of the b axis now runs horizontally and 

 is formed by the meeting of the faces p (021) and p (021). 

 [Plate VI, figs. 2, 4]. The three pinacoids are here repre- 

 sented, although b (010) was observed on only two of the 

 crystals, and then as a mere line face. The base is always 

 present, usually as along narrow face. The orthopinacoid 

 a (100) is large and slightly striated parallel to its inter- 

 sections with m (110) and the orthodomes; there is some 

 oscillation between a and m. The prism m is much less 



