36S PROCEEDINGS OF SECTION C. 



usually occur near the western coast, especially in Dusky and Breaksea 

 Pounds. At the entrance to Milford Sound they are denser and more 

 distinctly banded than elsewhere.- 



In the Darran Mountains, to the north and east of Milford Sound, 

 there is a large mass of mica norite. The diallage, which is abundant, 

 has the pleochroism and the schiller structure of hypersthene. The 

 mica is frequent — a deep brown biotite. 



The Bluff Hill and the Eound Hill of Orepuke are chiefly composed 

 of norite. The hypersthene in this case does not show schiller structure, 

 and is very largely changed to hornblende. The Rev. R. Baron con- 

 siders that all the hornblende in this rock is secondary. 



At Anita Bay, Milford Sound, a magnesian intrusion occurs. The 

 main mass of it is a kataclastic dunite, which contains here and there 

 a little diopside. There are also large blocks of remarkably fresh hartz- 

 bergite, in which the enstatite contains a little magnesite. In some 

 specimens the magnesite completely replaces the enstatite, and the rock 

 becomes marble-like, a granular mixtm-e of magnesite and olivine. 

 The magnetite of this rock contains 10 per cent, of chromium oxide. 

 Some of the boulders are pure enstatite rock. Much of the mass is 

 altered to serpentine and talc. 



Throughout the length of the South Island masses of plutonic rock 

 crop out on the western side of the divide. The nearest portion of 

 these to the mass already described is a peridotite area. On the western 

 side at least diorite forms the border of this area ; gabbro, pyroxenite, 

 and therzolite constitute its greater portion. The gabbro is coarse- 

 grained ; its felspar is almost completely changed to an isotropic sub- 

 stance whose exact nature has not yet been investigated. The pyroxenite 

 is a pure diallage rock of coarse grain. Much of the olivine in the therzo- 

 lite is kataclastic. There is probably pure dunite as well, for its half 

 serpentinised form constitutes a large mass of rock. 



This peridotite area, according to Professor Ulrich, stretches 50 

 miles or more to the north-east. According to his description the 

 rocks of this extension are much the same as those just mentioned. 

 In addition, Ulrich proved the highly interesting fact that awaruite 

 occurs in this rock mass. 



Further northward the plutonic rocks are almost exclusively 

 granites, varying in color from pink to grey, generally porphyritic, and 

 sometimes they carry tourmaline. At Separation Point there is a 

 great deal of sphene, and the porphp'itic character is marked. The 

 felspars weather out readily. They have the Baveno form, with large 

 development of the base and clinopinacoid and corresponding reduction 

 of the prism. Baveno twinning was not noticed. Occasionally the 

 ordinary form, with Carlsbad twinning, is found. 



The age of these plutonic masses is not definitely known. Hector 

 apparently includes them with the sounds area. Hutton thought 

 them much younger — certainly post-Carboniferous ; perhaps Jurassic. 

 Dr. Bell thinks them younger than his Arahura series of perhaps Car- 

 boniferous age. The pink granites of Preservation Inlet should perhaps 

 be included here, as they are said to penetrate Maitai (Carboniferous) 



