74 MARIE BENTIVOGLIO. 



N (241), M (8.15.4,), and R (13.17.6). The form N occurs 

 several times on both portions of the twin, a small irregu- 

 larly shaped face, while M and R occur only on the larger 

 segment. R is a long narrow face, M is relatively large, 

 almost replacing IV, which is correspondingly small where 

 these occur together. JV, M and R are extremely unusual 

 forms, and have been described by Borgstrom in cassiterite 

 crystals from Pitk'aranta. 1 The forms observed are listed 

 in the table above showing their measured and calculated 

 </> and p. 



STANTHORPE, QUEENSLAND, (Figs. 9, 10.) 

 This crystal is by far the largest examined, measuring 

 1*2 x 1 cm. in the direction of the c and a axes respectively. 

 It is doubly terminated, the primary pyramids s (111) being 

 very prominent, and the e (101) faces almost entirely 

 absent. Two parallel a faces (100) (100) are very large, 

 thus giving the crystal a tabular habit; the faces of the 

 prism zone are relatively small and striated. The crystal 

 is dark, with distinct lustre, but it is not in a good state of 

 preservation, and it is feared that some small faces along 

 the edges have been lost. The reflections, generally, were 

 satisfactory, and the readings reliable; a table of angles is 

 omitted as it is not considered necessary. The large 

 crystal supports at one end a very small crystal in twin 

 position, and a distinct feature is the oscillation which has 

 occurred during development from one segment to the 

 other, as seen on the prism zone. This zone in the large 

 crystal is cut by the prism zone of the small twin (fig. 9); 

 and it is noteworthy that the a face is present on the lower 

 portion of the prism zone and absent from the upper. More- 

 over this also applies to the twin which is divided by the 

 upper portion of the prism zone of the first crystal. 



1 Zeitschrift fiir Krystallographie, Band 40, 1905, pp. 1 - 12. 



