38 Transactions. 



it is also included within it, a structure already noted typical of the 

 crystalline schists. There is also evidence for a slight cataclasis in the 

 section. 



A still paler variety of hornblende may occasionally be seen in this 

 rock, occurring in almost colourless fibrous forms with beautiful poly- 

 synthetic twins. Further study would be necessary to prove whether 

 this is due to bleaching, to recrystallization of coloured hornblende 

 with separation of iron-oxides, or to uralisation of previously existing 

 pyroxenes. 



In No. 2 the feldspars predominate greatly over the darker minerals. 

 They give evidence of considerable crushing in strain shadows, bent twin 

 lamellae, and local cataclasis. Often irregularly disposed grains are included 

 in the larger crystals. Both coarse and fine albite lamellation may be 

 observed, while pericline twinning is rare. Probably more than one variety 

 of feldspar is present, and, indeed, the larger crystals show gradual zoning 

 from the centre to perijDhery, but the prevailing species appears to be andesine. 

 Delicate colourless needles are often abundant in the feldspars, and seem 

 to be sillimanite. Beyond these the feldspars show little sign of alteration 

 with the exception of rare grains of epidote or zoisite, and flakes of chlorite 

 which have probably migrated from the ferromagnesian minerals along 

 cracks. The hornblende and iron-ores occur in small patches of individuals 

 with such ragged contours that the structural relations to the feldspars 

 cannot be made out. The cores of the hornblende crystals generally consist 

 of a paler variety in optical continuity with the green exteriors, so that the 

 former presence of pyroxene is suggested. This small collection of rocks 

 is yet sufficient to show that there is a considerable diversity of rocks in 

 Bluff Hill. It would be exceedingly valuable to have a detailed examination 

 of this area made, as the phenomena observed are probably common to a 

 large part of Stewart Island, if not also in the Sounds region, and Bluff Hill 

 is a much more easily accessible region. The relative ages of the difierent 

 rocks, the mode of origin of the foliation, whether arising during or after 

 consolidation, the origin of the rock-variations and " basic secretions," 

 whether by pure differentiation or differentiation combined with absorption 

 as in Skye, are a few of the problems presented for solution. Probably 

 many analogies will be found with the Lizard district of Cornwall, on which 

 the Geological Survey of Great Britain is shortly issuing a detailed 

 memoir. 



Part III. — Waikawa. 



The last rock is an isolated beach-pebble picked up at Waikawa, and 

 possesses interest as being a type not hitherto, recorded in New Zealand. 

 The other beach-pebbles consist mainly of microgranites derived from the 

 Triassic conglomerates, but from its soft nature it is more probable that 

 this rock has come from a neighbouring intrusion. It shows a rich 

 mineralogical association, consisting of amphiboles, biotite, muscovite, 

 clinozoisite, epidote, two varieties of chlorite, talc, magnetite, and pyrite, 

 but hornblende is so abundant as to render the designation " lustre- 

 mottled hornblende rock " applicable. 



The hornblende occurs chiefly in large poecilitic plates of a pale-brown 

 variety, passing gradually to a pale-green on the exteriors. The minerals 

 enclosed poecilitically are feldspar and secondary minerals, partly after 

 feldspar and partly after some ferromagnesian, while there are chloritic 

 areas with sphene, which may simply represent alterations of a hornblende. 



