410 PROCEEDINGS OF SECTION ©. 
Omeo district. This rock has, however, been in so far meta- 
morphised that it has become foliated to some extent. The 
alternating foliatures with the felspars are of quartz, with also a 
colourless, very fibrous mineral, which appears to be fibrolite. 
The schorl is in rather narrow prisms. 
Mica schists of the character described extend up to nearly 
1000 feet above the river, where the schists are composed of 
foliatures of black mica, felspar and quartz. In places the 
foliatures contain small masses of felspar and quartz, forming 
“eves.” The foliatures vary from very narrow to a width of 
several inches of each mineral aggregate. This rock is a pressure 
schist, representing a former massive plutonic rock, composed of 
orthoclase (microperthite), biotite and quartz. At the summit 
of the spur, 1250 feet, which is nearly also at the summit of the 
Great Dividing Range, there is a well-marked example of one of 
the diorite-gneisses of this district. This place is well within 
the metamorphic area. This gneiss shows in the clearest manner 
the violent movements to which it has been subject after its 
consolidation, as well as an original gneissic structure due to the 
parallelism of some of its constituents. This gneiss is therefore 
interesting as being an example of both forms of gneiss. That, 
namely, which is frequent in the margins of the plutonic masses, as, 
for instance, at Swift’s Creek and which has been produced during 
consolidation. Secondly, that which has been produced in massive 
rocks after consolidation, by the effects of pressure metamorphism. 
The biotite mica is dark coloured, and is in crystals which have 
been bent, twisted, and in places opened out. It forms in great 
part the separations between the other minerals, thus producing 
a gneissic structure. Its position in the rock shows that it was 
formed after the porphyritic felspars which it surrounds. The 
felspars are triclinic, the angles have been somewhat rounded, and 
the crystals are more or less fractured or crushed. The broken 
fragments have in places been pushed aside, and the interstices 
cemented with quartz. The quartz is in considerable amount, and 
has been much granulated by movements in the rock. 
This gneiss is evidently somewhat later in age than the 
generality of the gneisses in which it occurs, and has been 
therefore less metamorphised than they. As a contrast, I may 
note the structure of one of the latter. The main mass of the 
rock is formed of foliations composed of fragments of felspar and 
quartz, with plates of biotite. The partings are formed of 
narrow foliations of a pale-coloured mica in minute scales and 
fibres, which appears to have resulted from the alteration of the 
finer detritus. In this mass, and surrounded by the foliations 
of smaller material are what have once been porphyritic crystals 
of triclinic felspars in the original quartz diorite; these gneisses 
are good examples of the pressure schists of the district. 
In this section there are several points to note. First, the 
