Speight. — Geology of the West Coast Sounds. 263 



Gneiss (G 11). — A white rock with a few large flakes of biotite. The 

 rock is almost all feldspar (oligoclase), some quartz, and muscovite in ragged 

 flakes. The feldspar has schiller inclusions regularly arranged parallel to basal 

 and brachypinacoids, and contains irregularly disposed areas of microcline. 



Diorite Gneiss {G 18). — A dark-coloured, rather fine-grained, distinctly 

 foliated rock. Under the microscope the rock appears even-grained, more 

 than half composed of hornblende and biotite, with both, especially the mica, 

 in rudely parallel arrangement. There are colourless grains of epidote, and 

 spheue in numerous grains. The quartz and plagioclase are in about equal 

 proportions. 



Diorite Gneiss (G 7).— Similar to G 18, but more basic. This is a schistose 

 rock with distinct foliae of feldspar and dark minerals. The feldspar is 

 oligoclase, accompanied by a little quartz. There is much hornblende and 

 biotite, the former more important ; occasional epidote ; and numerous 

 grains of sphene, both dark and pale coloured. 



Bligh Sound. 

 These rocks were collected on the north side of the river entering the sound. 



Hypersthene Diallage Gneiss (B 1). — A pinkish-grey rock,*distinctly foli- 

 ated. The feldspar is clear ; there are grains of quartz, hypersthene with 

 characteristic pleochroism and straight extinction, also diallage, and a little 

 biotite and ilmenite. Dr. Marshall has pointed out to me the resemblance 

 between this rock and a mica norite from the Darran Mountains, Milford 

 Sound (14). Both rocks contain the same minerals, but on comparing 

 slides his specimen appears more basic, and is without the gneissic structure 

 so markedly exhibited by the rock from Bligh Sound. This occurrence 

 may, however, be a gneissic variety of the mica norite./ 



Diorite Gneiss (B 2). — An indistinctly foliated rock. The feldspar is 

 oligoclase in broad plates with faulted and bent lamellae, at times crowded 

 with inclusions of epidote needles and crystals, similar to the rock from 

 the Bowen Falls mentioned by Marshall. There are corroded crystals of 

 hornblende, sometimes with schiller-like inclusions parallel to the base, and 

 filled with grains of quartz [quartz de corrosion) ; a small amount of other 

 quaiiiz also present, and numerous large individuals of epidote and flakes 

 of biotite. There are grains of ilmenite surrounded by aggregates of sphene 

 which are evidently formed from it. 



Hypersthene Amphibolite (B 3). — This is a dark-green rock, which ap- 

 pears under the microscope to be composed principally of greenish-brown 

 strongly pleochroic hornblende, with schiller-like inclusions ; some of this 

 may be altered augite. There is a considerable quantity of hypersthene, 

 a little olivine and augite. A small amount of oligoclase occurs, and much 

 rutile in grains. The rock was not found in situ, and it may be a basic 

 variety of a diorite found in the locality, but it shows no foliation or parallel 

 arrangement of the elements. The rock is related to a cortlandtite ; but 

 there is little olivine present, and this is not in poecilitic grains as in a typical 

 cortlandtite, but wedged in between the hornblende elements. 



Diorite (B 4). — A rock formed of equal parts of feldspar and dark con- 

 stituents, not distinctly foliated. In section it is composed of oligoclase, 

 a little quartz, much epidote, a fair amount of greenish-brown hornblende, 

 some biotite, and grains of sphene. It is an even-grained directionless rock, 

 with little, if any, sign of pressure. 



