Worth. — Petrological Notes on South Victoria fjcind liocks. 489 



bounded grains, some of which have been cracked and then parted by 

 considerable belts of gvoundmass. There appear to be no fluid inclusions. 

 Quartz-felsite. 



Black Island, 4. — Very pale-grey fine-grained sajidstone, with marked 

 banded structure, twelve bands in 7-5 mm. Rounded quartz-grains, with 

 more rarely a fragment of feldspar. Inclusions of apatite, zircon, and 

 dark mica occur in the quartz. There are also numerous fluid inclusions 

 with bubbles, the inclusions large and the bubbles of very varied size. The 

 cementing-material is silica. 



Black Island, 5. — Fine-grained granular quartzite, breaks in thin slabs ; 

 colour red-brown. Well-rounded grains of quartz, with an occasional more 

 angular feldspar ; the latter in some instances is microcline. The red 

 colouring-matter is confined to the outside of the grains. Mineral inclusions 

 in the quartz are very rare. The fluid inclusions are not numerous, and 

 are very small. To all appearance the materials of this quartzite are de- 

 rived from a different source from that of Black Island, 4. The cement- 

 ing silica is frequently, but not invariably, in crystal continuity with the 

 adjacent quartz-grain. 



Black Island, 6. — Purple-grey rock, breaks in thin slabs, very fine 

 texture. Minute, very confused structure, even the feldspar laths being 

 but rarely well defined. The larger feldspars are nearly all mere patches, 

 without crystal outline. All are cracked and yellow-stained along cleavages. 

 The mineral may be labradorite, but its determination is difficult. Small 

 irregular prisms and grains of pale-green augite are very common, and 

 occur not only in the groundmass, but also as inclusions in the feldspar. 

 Some few larger augites are now almost entirely replaced by magnetite. 

 There is a fair quantity of magnetite and somewhat more of granular sphene 

 scattered throughout the slide. Camptonite. 



Black Island, 7. — Very fresh-looking rock of somewhat minutely dioritic 

 texture, dark grey with light grain. The groundmass an irregular coarse 

 matwork of plagioclase, clouded slightly in places, but for the more part 

 clear, the forms comparatively short, probably labradorite. There is 

 some magnetite, chiefly associated with augite. Large plates of augite, 

 almost entirely diallagic, in shades of olive - green. Augite - diorite 

 (gabbro). 



Black Island, 8. — A mottled rock in dark purple-brown and black. 

 Weathered surface presents appearance of flow structure. Precisely similar 

 rock found at first camp. A very fine-grained rock of confused nature. 

 Consists apparently of ill-formed feldspar laths, small ill-formed prisms, 

 • and grains of pale-brown augite, magnetite, sphene, a little interstitial 

 calcite, and an undetermined zeolite. The zeolite has too-high double 

 refraction for analcime, and it with the calcite joins to form an irregular 

 patch, around one end of which the feldspar laths are well defined and lie 

 parallel to its margin. From half-way up North Peak, not in situ. Camp- 

 tonite. 



Black Island, 9. — Pink granular felsite, spotted with dark green. 

 Porphyritic quartz and feldspar, but no well-formed crystals. Much 

 micro-pegmatite, which is the prominent feature of the' slide. Some of 

 the feldspar is clouded, some striated. Practically all the quartz areas are 

 in mosaic. There is a little green hornblende in grains and blades ; the 

 hornblende is to a great extent broken down to a dark-brown product, with 

 the apparent production of some epidote. Hornblende micro-pegmatite. 



