BY W. F. PETTERD, C.M.Z.S. 165 



evidence of decomposition, the mass becoming much softer 

 in consequence; on the faces of fractures and on the walls 

 of cavities in this partially-altered ore are sparingly 

 scattered small spangles of an extremely thin white mineral 

 which has a highly glistening lustre, and which, from its 

 physical characters, would appear to be zincaluminite, but 

 the scales of the attached substance are so extremely thin 

 that it is difficult to secure sufficient for a 'satisfactory 

 qualitative test. 



" Sphalerite is often found w^ell crystallised in the Zee- 

 han district. Some of the crystals in the western portion of 

 that field (Comstock) are well formed, consisting of sup- 

 plementary tetrahedra, so that perfect smooth-faced octa- 

 hedra result occasionally. In other cases the tetrahedral 

 faces are striated in the charact'eristic manner. Simple 

 twins occur in which the twinning-plane and combination- 

 plane are identical with a tetrahedron face. In such cases 

 as those in which equally-developed supplementary tetra- 

 hedra are twinned according to this law, the resultant twin 

 crystal closely resembles one of the characteristic twins 

 of a mineral in the spinel group. These crystals of 

 the Comstock district are black and opaque. . . . ^. 

 On the Silver King-Bell line of lode at Zeehan the vein- 

 matter often carried massive ruby and resin blende, and 

 occasionally crystals occur in the vughs. These crystals, 

 usually brown in colour, are not so perfectly developed as 

 those of the Comstock district. ... To the north of 

 Zeehan, in the area drained by Parting Creek, there is a 

 notable development of sphalerite crystals which are 

 almost invariably pale in colour — from yellowish-brown to 

 yellow. These crystals are highly complex forms and are 

 often distorted." (L. K. Ward.) 



Dr. C. Anderson, M.A., D.Sc. (Edin.), has supplied the 

 following notes upon some rare sporadic sphalerite crystals 

 which were obtained at the Heazlewood Silver-lead 

 Mine : — 



'' The crystals measure up to '8 cm. in diameter, and 

 have a brilliant, almost metallic, lustre on some of the 

 faces. They are accompanied by siderite in sharp-edged 

 crystals. The largest crystal was measured on the gonio- 

 meter, and found to be a complex quartet, consisting of 

 one large individual with three smaller ones twinned on 

 different tetrahedron faces, and partly in juxtaposition, 

 partly inter-penetrating. The forms are a (100), d (110), 

 o (111), m (113), g, (331); in addition there are certain 

 dull planes not admitting of exact ansular measurement, 

 but which seem to belong toj3i (522). The largest faces 



