64 Rocks of Noyang. 



The lime-mica which is here indicated may perhaps be 

 included in the minute scaly aggregates. Disregarding the 

 small amount of apatite, considering the ferric hydrate as 

 extraneous, and including the small amount of chlorite with 

 the mica, we have the following composition of the rock : — 

 Micaceous minerals ... ... ... ... 62 - 63 



Quartz 37-37 



100-00 

 — the micaceous minerals being, to the quartz, in the 

 molecular proportion of 1*46 : 1* 



The Omeo road from Noyang follows, for some distance, 

 the contact of the sedimentary and igneous rocks along 

 Navigation Creek. The alteration here is mainly an indura- 

 tion, thereby producing a hard flinty-looking rock, differing 

 in appearance somewhat from the normal hornfels. On 

 examining a thin slice, I found it to consist almost entirely 

 of grains of quartz of different sizes, even down to mere dust. 

 With this there was a very little brown mica. Many of the 

 larger quartz masses were not only compound, but increased 

 in size by secondary quartz which, also generally diffused 

 through the rocks, gives it its indurated appearance. At the 

 foot of the Fainting Range, however, the quartz-mica-por- 

 phyrite mass has produced much more marked effects — that 

 is, if one can be quite sure that the alteration is wholly due 

 to its influence, and not in some measure to previous meta- 

 morphism ; for it is on the northern side of this range that 

 the schists commence to assume an appearance which is more 

 like that of the less metamorphosed members of the 

 regional schists, than those contact rocks which I have 

 described herein. 



At the summit of the Fainting Range the sedimentar}?- 

 rocks have a wrinkled schistose structure, the bedding verti- 

 cal on a strike of N 70° W. This character is maintained 

 down the range southwards to near their contact with the 

 quartz-mica-porphyrites, where the dip of the schists is to 

 N 10° E at 75°. They are penetrated at this place by 

 several large dykes proceeding westward from' the igneous 

 mass. 



I prepared several samples from this contact, and I found 

 them to be somewhat peculiar forms of hornfels. One sample 

 was composed mainly of angular quartz grains, set together 

 with only slight traces of bedding in a material which had 

 been altered to a micaceous mineral in aggregates of minute. 



