Metamorphic and Plutonic Rocks at Oraeo. lOD 



prism. These samples of the schists sufficiently describe the 

 character of all the beds shown in the section, the onl}^ 

 difference being that some are more nodular than others, or 

 that in places the quartzose beds predominate over the 

 micaceous ones, or vice versa. 



An inspection of the diagrams given, which sufficiently 

 well copy the reality, shows that the schists have been 

 invaded by the granites, which, in places, fill spaces at one 

 time occupied by the schists, and in other places, at furthei- 

 distances, have penetrated between the beds and more rarelj^ 

 across them. Where the contact line is well marked, the 

 schists are cut across, and the granites abut against tlie 

 truncated ends, and also include fragments of the beds 

 which have been detached, and have become surrounded by 

 the magma. The general character of these granites in mass 

 is a rather coarse crystalline, or crystalline granular 

 compound of felspar, muscovite, and quartz, analogous to 

 that described previously at p. The dykes and veins which 

 lie between the schist beds are, however, as a rule, much 

 coarser in structure than the granite masses, and may, in 

 some cases, be rightly designated as Pegmatite. But since 

 this name has, to some degree, become associated with the^^ 

 conception of dykes which are not, strictly speaking, igneous 

 and intrusive*, it may be well to use the general term 

 " muscovite granite." These dykes vary in the locality" 

 taken as an illustration from G inches up to 36 inches in 

 width. With the larger ones I found quartz veins to be 

 associated, thus recalling the " plutonic quartz veins " which 

 I have spoken of elsewhere -f*. In this locality these veins 

 seem so far to have proved entirely barren of gold or ores of 

 metals. In Fig. J, Plate II., I have sketched one of the 

 dykes of muscovite granite which occur in the section 

 described. I chose this dyke for the reason that it represents 

 the fair average sample, while at the same time it is, in 

 parts, not too coarse in texture for a thin slice for microscopic 

 examination. It is composed of felspars of two kinds, 

 muscovite mica and quartz. The potassa felspar is in 



* Kalkowsky remarks as follows : — " Es ist nun aber zu beachten dass 

 seiche Pegmatite fast stets ' gang granite ' sind, also massen dereu anogene 

 Entstehung zehr zeifelhaft ist die viel melir durch manclierlei cliemische 

 und mecbauische Processe unter uns nnbekannten Verbalt nisseu gebildet 

 ■worden sein mogen." — Elemente der Lithologie, p. 66, 



t Notes on the Area of Intrusive Rocks at Dargo. Transactions Eoyal 

 Society of Victorifi, Vol. XIII., p. 152. 



