SOME CRYSTAL MEASUREMENTS OF CHILLAGITE. 219 



It is possible that a small percentage of scheelite or fer- 

 gusonite molecules may be present, and this might account 

 for the low value of c. 4 Moreover the value c for chillagite 

 differs considerably from the range of values recorded for 

 stolzite or wulfenite. The values of c recorded for stolzite 

 are : — 



(1) 



1.5576 * 



(6) 



1.5613 : 2 



(2) 



1.5579 2 • 



(7) 



1.5631 2 



(3) 



1.5586 2 



(8) 



1.5667 * 



(4) 



1.5597 2 



(9) 



1.5692 5 



(5) 



1.5606 3 







For wulfenite the only values of c found were : — 

 1.7771 4 1.7774 6 



There thus appears to be some evidence in favour of the 

 crystals representing a new mineral, but more is needed 

 before this can be definitely established. 



Our thanks are due to Dr. C. Anderson of the Australian 

 Museum for advice in connection with part of the work. 



Explanation of Plates. 



Plate XV is the Stereographic Projection of most of the forms 

 found. A number of important forms have been omitted 

 to avoid confusion in the figure. The forms represented 

 by open circles are not so well developed as those represented 

 by the black dots. 



Plate XVI, fig. 1 is an Orthographic Projection of Crystal 2. 



Fig. 2 is the corresponding Clinographic Projection of Crystal 2. 



1 Zeit. f . Kryst. Vol. xliii, 1907. z Hlawatsch, loc. cit. 3 Hlawatsch, 

 Uber Stolzit and Easpit von Brokenhill, Zeit f. Kryst. Vol. xxix. * Zeit. 

 f . Kryst. Vol, xlv, 1908, p. 93. 5 A. Levy, On a tungstate of lead, Ann. 

 of Phill,, Neue Serie, xn, p. 364. 6 G-oldschmidt, loc. cit. 



