2. A reddish-brown vesicular rock, the vesicles lined with a pale- 

 green mineral. Section : Ground-mass dense with hajmatite dust. 

 The porphyritic minerals are plagioclase and enstatite. A chloritic 

 mineral infiltrates the felspars and enstatites ; the latter are often 

 decomposed into chlorite and a colourless aggregate with low 

 polarization colours. The vesicles are lined with a chloritic mineral 

 probably delessite, and tilled with a colourless mineral with dull 

 polarization colours, probably calcite. Hochstetter, New Zealand, 

 p. 261 ; Park, Kept. Geol. Expl. 1885, p. 156. 



IMensville, Kaipara. — A dark brown compact rock with small 

 yellowish felspars, not conspicuous, and occasional pyroxenes. S.G. 

 2-78. Section : Ground-mass moderate, crystallitic, globulitic, a 

 brown glass thick with haematite dust. The porphyritic minerals 

 are plagioclase, augite, enstatite, and magnetite. The plagioclase 

 is zoned, and goes to -04 in length. The augite is idioraorphic, 

 greenish-yellow, up to -06 in length. The enstatite is subordinate 

 to the augite, pleochroic, changing from yellow-brown to yellow- 

 green, goes up to -02 in length ; sometimes forms intergrowths 

 with the augite. 



Komiti Peninsula, Kaipara.— A greyish-black compact rock 

 with very small felspars and pyroxenes not conspicuous. S.G. 

 2-74. Section : Ground-mass moderate, crystallitic, longulitic, 

 the glass pale ; with some felspar microlites and abundant mag- 

 netite grains. The porphyritic crystals are plagioclase, augite, 

 and enstatite. The plagioclase is in imperfect crystals, rarely 

 over -04 in length. The augite is pale greenish, up to -02. The 

 enstatite is pleochroic, changing from vellowish-brown to bluish- 

 green, up to -03. Park, Rept. Geol. Expl., 1885, p. 167, and 

 1886-7, p. 220. 



Whangarei Heads. — A rather pale grey rock with scattered 

 crystals of pyroxene. S.G. 2-66. Section : Ground-mass abundant 

 microlitic, composed of felspar laths, up to -01 in length, closely 

 meshed, with augite in grains and prisms, and magnetite in grains. 

 The porphyritic minerals are plagioclase, augite, enstatite and 

 magnetite. Secondary constituents are a little quartz and mag- 

 netite. The plagioclase crystals are few and much decomposed, 

 up to -04 in length. The augite is pale brownish-green, idiomor- 

 phic, up to -04 in length. The enstatite preponderates over the 

 augite, pleochroic, changing from reddish-green to bluish-green, 

 up to -04 in length. 



Olivine Andesite. 



Bank's Peninsula. — 1. A pale grey vesicular rock, witli con- 

 spicuous felspars and black hornblendes and ausrites. Section : 

 Ground mass abundant, microlitic, of teKpir lath- and pi it( - frt)m 

 •0U7 to -01 in length, with grains of augite, .uul m uiu^tit. , and 



