362 A. J. Moses — Crystallization of Molybdenite. 



tals of green amphibole. On one crystal showing four faces 

 of a pyramid two adjacent faces intersected in an edge which, 

 permitted careful adjustment on the Fuess goniometer. Each 

 yielded a bright image of the signal which was only slightly 

 distorted horizontally. The ^.ve readings of each face varied 

 with respect to the mean, to the nearest half minute as follows : 



First. Second. 



+ H -6* 



+ 8i ~8i 



+ H +6| 



— 5^ +8-2 



The angle obtained was 54° 08', which corresponds_ to an 

 angle with the cleavage of 65° 31/. The angle for (1011) on 

 the Frankford, Pa., crystals is 65° 35'. 



6. Molybdenite from Warren, IV. H. 



In an old suite of molybdenite specimens in the Egleston 

 Museum I found a number of small doubly terminated crys- 

 tals three of which gave with the hand goniometer for all 

 faces an angle with the cleavage between 54° and 55°. The 

 pyramidal faces were striated and most of them curved and 

 the cleavage was curved. 



One crystal (fig. 4) showing twelve pyramidal planes was 

 roughly 'oriented on the two-circle goniometer by the bent 

 cleavage. Three faint signals were obtained with (f> respec- 

 tively 60°, 120° and 240°, which were approximately p = 90°. 

 The crystal was then readjusted until these signals were accu- 

 rately p = 90°. 



The results were analogous to those obtained with the Aid- 

 field crystal, that is images of the collimator signal were 

 obtained for two different positions, each of which corre- 

 sponded to a general illumination of the surface. In this case, 

 however, both corresponded to oblique angles (pyramids). The 

 results were 



<p p p 



0° 55° 15' Two images 64° 36' 



60 54 30 Bright image 64 58 



119 06' 



180 24 Blur 



240 20 54 25 Blurred image 64 18 



Average 54° 43' 64° 27' 



The simplest interpretation of these angles is that they corre- 

 spond to (2023) and (1011), for which the corresponding calcu- 



