498 Transactions. 



Hector, in his " Outline of the Geology of New Zealand," 

 in 1886, describes the rocks as crystalline schists, but he does 

 not give a definite age to them, though he suggests a correla- 

 tion with Humboldt's gneiss-granite series of South America. 

 He says that the basement rocks are foliated and contorted 

 gneisses associated with granite, syenite, and diorite, while round 

 them wrap hornblende schist, clay slate, and other rocks, probably 

 metamorphic representatives of Devonian age. 



The only actual descriptions I can find are due to Hutton,* 

 who mentions granitite from Port William, Stewart Island ; 

 syenite from Preservation Inlet and Wet Jacket Arm ; biotite- 

 pyxoxenite from Dusky Sound ; chloritic pyroxenite from 

 Martin's Bay ; and serpentine from Big Bay. 



Seeing that so few accurate rock-descriptions have hitherto 

 been published, it has been considered advisable to put on record 

 the following notes on rocks collected at various points in the 

 Sound region indicated in the map (Plate XXI). The results of 

 the examination of the various specimens collected justifies the 

 following general statements. 



The prevailing rocks are gneisses containing but little 

 quartz, much feldspar, some p\Toxene hornblende, or biotite, 

 and often garnet. At Half-moon Bay, Stewart Island, there 

 is abundant hornblende. Irregular basic patches are numerous. 

 The rock is here a diorite gneiss. At Golden Bay, a mile dis- 

 tant, granite outcrops, and there is a thick vein of graphic 

 granite with microcline — microperthi te. At Ruggedy Point there 

 is a large intrusive mass of granophyre whose resistant nature 

 causes it to form outstanding rugged pinnacles and cliffs. At 

 Preservation Inlet there is a pink granite (syenite, Hutton) which 

 apparently is intrusive in the spotted slates of that locality. 

 At Dusky Sound there is a muscovite gneiss with little quartz, 

 but with muscovite in plates often 2 in. across. At Duck Cove 

 pyroxene gneiss with much garnet is the most frequent rock, 

 but there are basic secretions of amphibolite and an altered 

 crushed pale-g-reen rock in which epidote and quartz form with 

 a little feldspar the whole rock. At Breaksea Sound the pATOx- 

 ene gneiss is the most abundant rock. In Doubtful Sound an 

 amphibole schist occurs at Blanket Bay, and the same rock is 

 found at Dea's Cove, Thompson's Sound, where a typical gneiss 

 also constitutes a large rock-mass. At Milford Sound there is 

 a peridotite intrusion! with gneissic rocks all round it. The 

 enstatite of one of the hattzbergites is here in places entirely 

 altered to a carbonate, and the rock appears a pure-white marble, 

 though in section olivine is found to constitute a fourth of it. 



* Trans. Roy. Soc. N.S.W., vol. xxiii, p. 112. 

 t Marshall, Trans. N.Z. Inst., 1904, p. 481. 



