406 



RECOKDS OF THE AUSTKALIAX MUSEUM 



A more complicated twin is drawn (PI. Ixxv., fig. 3) 

 in ortliograpliic projection ; here we have a relatively large 

 crystal with four smaller individuals twinned to the former 

 on (101). As the four smaller crystals are essentially 

 similar the group has been idealised in the drawing. The lower 

 surface consists of the s faces of the main crystal and one very 

 small individual in twin position. The colour is black and the 

 faces are as a rule smooth and brilliant, yielding excellent reflec- 

 tions. The dimensions are approximately -75 cm. (parallel to 

 vertical axis) X 1 "00 cm. 



The measured and calculated angles are given below : 



Hogue's Creek, near Duxdee, New Soutpi Wales. 



(Plate Ixxv., fig. 6). 



Hogue's Creek furnishes good tinstone crystals with the usual 

 stout prismatic habit, sometimes simple, sometimes twinned ; a 

 fine example of a simple crystal yielding the forms a, m, r, h, s, z, 

 is here figured. The faces of r are narrow, the pyramid s is large 

 and striated parallel to its intersections with e. Dimensions 

 approximately 1x1 cm. 



The Glen, New England, Neav South Wales. 

 (Plate Ixxv., fig. 5). 

 A rather large crystal, about 3 X 2-5 cm., from this locality 



