MTNERALOGICAL NOTES: No. V.— CASSITERTTE 



CERUSSITE, ZEOLITES and other AUSTRALIAN 



MINERALS. 



By C. Andekson, M.A., B.Sc, .Miiieialooist. 



(Plates Ixxv.-Ixxx.). 



CASSITERITE. 



Emmaville, New South Waleh. 



(Plate Ixxv., %. 1). 



The crystal of cassiterite from this locality here figured is of 

 interest as having an acute pyramidal habit through predominance 

 of the di-tetragoiial pyramid z (321) ; it resembles the needle or 

 spai-able tin of the Cornish miner, a tj^pe which seems ver'v rare 

 in Australian cassiterite. The prism faces are strong) v striated 

 owing to oscillatory combination between m (110) and r (-30), r 

 however being subordinate. The crystal measui-es 1*25 x "75 cm. 

 The part bounded by the prism faces is mainly black with patches 

 of semi-transparent "ruby tin," the apex of the crystal down to 

 the faint line traversing the faces of z, a little below and parallel 

 to its intersections with s, is black with metallic lustre, wliile the 

 central part is reddish and ojjaque. From this curious distribu- 

 tion of colour the probable hist(jry of the crystal may be deduced. 

 Thus it may be inferred that it was at first prismatic in habit, 

 most likely terminated by .s- (111), and of a black colour. With a 

 change in composition (indicated by the cliange in colour) the 

 prism ceased growing and the pyramid z predominated : finally 

 came another change in composition at a time when tlie ci'vstal 

 had assumed nearly its present habit. 



