Speight. — Geology of the West Coast Sounds. 261 



morphic needles, occasional grains of sericitised feldspar packed in between 

 the hornblende ; a t-mall amount of yellowish epidote also occurs. 



Gneiss (D 16). — From Duck Cove. A markedly schistose rock, showing 

 the effects of pressure plainly in the hand-specimen. The structure is 

 completely cataclastic, the rock being composed of grains of quartz, micro- 

 cline, and feldspar showing strain-effects ; brown mica occurs in well-marked 

 parallel arrangement. 



Gneiss (D 17). — From Duck Cove. This is the same as Marshall's G 13. 

 It is composed of much quartz in irregular grains, plagioclase and microcHne, 

 biotite and muscovite in about equal proportions, the latter sometimes 

 crowded with needles of sillimanite ; the structure is cataclastic. 



Gneiss (D 18). — From Duck Cove. A greenish- white rock completely 

 crushed to a fine aggregate of feldspar and quartz, with a few larger parti- 

 ally sericitised crystals of feldspar ; there are a few larger quartz grains 

 still left, and numerous flakes of muscovite in parallel arrangement. 



Mica-schist (D 5). — From Pickersgill Harbour. This is a dark compact 

 rock, not showing schistose structure in the hand-specimen. In section it 

 appears as a fine-grained rock composed of brown mica in small irregular 

 flakes and small grains of quartz, with muscovite laths in rough parallel 

 arrangement ; small black grains of iron-ores in aggregates and strings are 

 extremely common. This rock closely resembles a mica hornfels, and is 

 probably due to the effect of a granite intrusion. 



Gneiss (D 6). — From Pickersgill Harbour, The rock exhibits well- 

 marked schistose structure. It is composed of much quartz ; feldspar, 

 both twinned and unt^vinned ; occasional microcline ; dark and light mica, 

 sometimes intergrown ; aggregates of epidote grains ; ilmenite ; apatite 

 in short needles. Granophyric structure is common, and the whole rock 

 shows the effect of pressure. 



Daggs Sound. 



The only type of rock found on this occasion in Daggs Sound was a 

 gneiss (G 1) exhibiting marked schistose structure, white in colour, but 

 speckled with greenish hornblendes. Under the microscope it proves to be 

 a diorite gneiss. It contains the following minerals : Much oligoclase, 

 frequently showing strain-effects, hornblende in corroded crystals, green in 

 colour, and altered to aggregates of epidote and chlorite. Epidote also 

 occurs along the cleavage-planes of the feldspar and as numerous grains and 

 aggregates. Ilmenite occurs freely as grains, and at times forms irregular 

 granular masses. Occasional mica and interstitial quartz also occur. The 

 structure is moderately cataclastic. 



Thompson Sound. 



Collections were made at Wood Head, at the head of Gaer Arm, and 

 at Deas Cove. 



Diorite Gneiss (G 2). — From the head of Gaer Arm. In the hand-speci- 

 men this is a yellowish-white rock with speckles of dark-green hornblende, 

 indistinctly foliated. Under the microscope it exhibits an even-grained 

 texture, with occasional strain-effects. The feldspar is an albite-oligoclase, 

 often micrographically intergrown with quartz ; quartz is present in quan- 

 tity, sometimes intergrown with hornblende ; hornblende, greenish-brown 

 in colour, is a very prominent constituent ; biotite occurs in broad plates, 



