Metamorphic and Plutonic Rocks at Omeo. 115 



The main mass of a slice prepared from a sample of tlie 

 quartzose variety I found to be composed of almost equal 

 sized grains of quartz and felspar, the former being the 

 more plentiful. There are also here some grains of quartz 

 of much larger size than the average, and these are all 

 much broken. All the quartz grains, large and small, have 

 numerous fluid cavities, and also include numerous small 

 reddish -brown flakes of mica. 



By far the greater number of the felspar grains are simple, 

 and appear to be orthoclase. The few which are compound 

 I consider to be oligoclase near to albite, if not indeed the 

 latter. They much resemble similar felspar grains which 

 occur in some of the quartzose schists at Ensay. 



In the mass of the rock which is thus composed of quartz 

 and felspar there is an amount of mica equal perhaps to 

 one-fifth of fche whole. The greater part of the mica is a 

 yellowish to light-brown magnesia mica, not strongly pleo- 

 chroic, the remainder beino^ muscovite. The mica lies 

 between and around the grains of quartz and felspar, and 

 has, as it seems to me, been formed later than either of 

 them. A few yellowish tourmaline crystals, with a few 

 small grains of magnetite, (?) complete the composition of 

 this rock. 



It is to be noted that in these schists, which adjoin an 

 intrusive mass or large dyke of aplite, felspar and tour- 

 maline appear, and that the schists generally have assumed 

 a structure and composition differing in a marked manner 

 from those at (a) which were taken as a starting point, 

 because they were a fair example of the mica schists which 

 extend from the Bo wen Mountains across towards Hinno- 

 munjie, and which are perhaps also representative of the 

 metamorphism of those strata generally anterior to that 

 further alteration which was produced by the gi^anites, 



(/.) There is here an exposure of a mass of granite. The 

 surrounding schists are much contorted, and are spotted and 

 micaceous. The sample of schist which I examined from 

 this place is fine grained, and composed of numerous grains 

 of quartz, among which are small flakes of a brown mica 

 and of muscovite. The mica has in places a parallelism, and 

 thus produces the appearance in the slice of foliation. A 

 few light-coloured grains of tourmaline complete the rock. 

 The granite is rather light-coloured, and is composed of 

 felspars, mica, and quartz. The principal felspar is orthoclase 

 in irregularly bounded crystals, which in some cases include 



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