114 Transactio7is of the Royal Society of Victoria, 



(e.) The schists at this place are very massive, no bedding 

 being visible and only indistinct foliation in the rock. 

 I found a sample, of which I prepared a thin slice, to be very 

 micaceous, most of the mica being a yellowish or colourless 

 alkali mica, the colourless portion being either in plates 

 or else in plumose or fan-shaped groups of plates. The 

 yellowish-coloured mica is fibrous, or is in small scales, 

 and it fills in spaces. This yellow fibrous mica also 

 surrounds other minerals, and seems to be due to later 

 alteration, and has some resemblance to damourite. There 

 are also numerous patches of pleochroic brown mica in 

 which I observed in places minute crystalline inclusions, 

 round which there is a dark to black halo which disappears 

 when the slice is rotated, so that the traces of the basal 

 cleavage are perpendicular to the plane of the polarizing 

 nicol The pleochroism of the halo is only visible in the 

 vertical sections of the mica, and not in those which are 

 parallel to the basal cleavage, in which the inclusion is 

 surrounded and concealed by a permanent circular opaque 

 black patch. In these latter sections the dark halo is seen, 

 but it undergoes no change in rotatiug the slice. In 

 connection with these phenomena are to be noted numerous 

 crystals and grains of iron ore, or possibly ilmenite, although 

 in no case did I observe any of the characteristic alteration 

 products of that mineral.* Many of these crystals of ore 

 can be recognised as being hexagonal, but in most cases the 

 outlines of the crystals are eroded or worn away; other 

 cases are where there are mere skeletons of crystals, part of 

 the form being indicated merely by minute black grains in 

 rows. These ores are connected in some cases with the 

 broAvn mica, and with the halos surrounding the microliths 

 of which I have spoken. These observations suggest that 

 the pleochroic halos may be due to local molecular aggrega- 

 tion of iron in the mica."|* 



As is usual in other parts of the district, there are two 

 alternatiuo^ varieties of these schists, one of which is more 

 quartzose than the other. 



* Minute portions of iron ore wliicli I extracted from the powdered rock 

 did not give me any reactions for titanium when examined with fluxes before 

 the blowpipe. 



t Eosenbusch notes these occurrences in mica, and suggests the above 

 explanation in his " Physiographie der Minerahen," 2nd edition, p. 192. 



