Orthodomes. — </> in distinction to types I and II is narrow- 

 while tr is large and smooth and gives excellent reflections. 

 Oisa large face— very striated, and gives a train of siginU. 

 the angle a a D varying between 80° 37' and 69° 54'. It 

 interoscillates with c, the latter appearing as a narrow 

 strip in the middle of D. </>, >/ and v are all well developed 

 and on this crystal show no striations at all. 



Clinodomes are again represented by J, f, and p. All are 

 ■nstriated and give excellent readings. The prism m and 

 the hemipyramid h are large and well developed as before, 

 s occurs as a large five-sided face, and the edge between 

 s and c is truncated by the hemipyramid P (223). The 

 latter is a very distinct trapezoid face, giving an excellent 

 signal, and has not been previously recognised on azurites 

 from Broken Hill. 



Crystals of this type have been described and figured by 

 Van Name and Penfleld.' In addition to the above forms 

 they recognised w (120), p (134), k 221 and B (241) but do 

 aot find <r (101) and P (223). Cesaro 2 has described a similar 

 crystal from Broken Hill possessing the characteristic 

 faces A and D. 



Summary.— The three types of crystals that were investi- 

 gated show a great similarity of habit. All possess the 

 same essential forms and the faces have practically the 

 same degree of development. Type II certainly seems to 

 he intermediate in position between types I and III, and 

 hence the mere possession of a couple of extra faces does 

 not seem to be sufficient to put the crystals into different 

 classes. Therefore looking at them from a broad point of 

 view, they are all practically of the same habit, viz., elon- 

 gated in'the direction of the b axis and more or less tabular 

 on the a pinacoid, which is always the largest face. 



. de 1' Acad. Roy. de Belg. 1905, ] 



