100 The Sedimentary, Metamorphic, 



In the upper part of Watts Creek there are numerous 

 examples of intrusive dykes. Some are quartz porphyrites, 

 others are basic dykes, which can only be distinguished from 

 each other by means of microscopic examination. One 

 such, which in appearance would formerly have been classed 

 as Aphanite, I found to be a Diabase porphyrite, having a 

 grouncl-rnass of light-brown basis, and exceedingly 

 numerous minute lathlike felspars. In this are short and 

 isolated stout prismatic crystals or groups of crystals of an 

 almost colourless augite, and a few large serpentine 

 pseudomorphs, which may have been olivine, but which 

 have not the marked rhombic outlines so frequently found 

 with this mineral. 



37. — This sample is taken from a mass of rock which fills 

 up the whole bed of Watts Creek, at a distance of about 

 half a mile from 36. • It is composed of orthoclase, a little 

 plagioclase, some chlorite and quartz, and a considerable 

 amount of pinite material, with its usually associated alkali- 

 mica. The felspars have been, as in many of the Ensay 

 Rocks, considerably broken and crushed. I feel myself 

 unable to determine whether this is a completely metamor- 

 phosed schist or an intrusive rock. Judging from its 

 appearance in situ I incline to the latter belief. 



Near this place there is a pegmatite vein composed of cleav- 

 able masses of yellowish felspar, glassy-looking quartz, and 

 silvery alkali-mica ; in fact, a typical example of a very 

 common class of veins, which occur in the Omeo district in 

 connection with the metamorphic schists, and less frequently 

 in other, parts of the mountains where there are contact 

 schists of the hornfels type. 



The felspar in this vein is in cleavable masses up to three 

 inches in diameter, and I collected an example of it for both 

 microscopic and chemical analysis. 



I prepared several thin slices in three directions, from 

 pieces struck from the most marked cleavage (OP), from 



others from the less perfect cleavage ooPco, and thirdly 

 from slices as nearly perpendicular to those two directions 

 as I could prepare them. 



Sections prepared from the most perfect cleavage show a 

 main felspar mass, which is, however, not homogeneous 

 throughout. It becomes obscured in different parts as the 

 slice is slowly rotated between the crossed nicols ; but these 

 areas are not sharply defined, but it is rather that the 



