68 
range, the metamorphosed rock, close to the intrusive, occurs 
as a fine-grained, compact quartzite, passing further from 
the contact into a garnetiferous gneiss, with large lenticular 
crystals of felspar (a variety of adularia, or moonstone), hav- 
ing a satin-like lustre, and which, even to the naked eye, can 
be seen to be locally surrounded by a layer of finely crushed 
material derived from the grinding down of the felspar itself 
(Morter structure ). 
Fig. 3. — Augen Gneiss, Mount Cockburn, Mann Ranges. 
In the former instance the altered rock was no doubt 
originally a somewhat massive, siliceous sandstone ; m the 
latter a finely laminated rock has probably been altered by 
minor injection of igneous matter between the planes of lami- 
nation (injection gneiss). 
South of Mount Cockburn, however, garnet-schist* and 
fissile gneiss occur at the zone of contact, while gneissic 
quartzites overlie the gneiss. It is in this locality that a 
natural section affords opportunity of studying the relative 
positions of these altered rocks. (Section on Plate xix.) A 
granitic intrusion appears in the form of a central axial-core, 
* W. C. Gosse writes that Mount Charles is "composed of crrey 
granite and skte." Report and Diary of Central and Westeni 
i ^'^ ui"^ Expedition, 1873. ParliamentaiT Paper No. 48, House 
Assembly, 1874, pa pre 12. No slate was obsei-ved in this neigh- 
bourhood, and it may be that Gosse mistook the schist or fissile 
gneiss for the same. 
