of felspar and hornblende, shewing fluxion. There are no trichites 

 nor niicrovesicles. The hornblende microlites are long narrow 

 prisms of green colour which extinguish at angles up to 20° with 

 their length. 



This obsidian was in common use by the Maories, and no doubt 

 the analysis of an obsidian from the Bay of Islands, given in 

 Phillips' Mineralogy, by Brook and Miller, refers to it. Silica 

 75-20, alumina 6-86, red ox. of iron 6-54, lime and magnesia 3-83, 

 soda and potash 7-57 ; S.G. 2-386. 



Taupo District—BUck. S.G. 2-37. Section : A homogeneous 

 pale glass with a few small felspar microlites, not shewing fluxion, 

 and rarely small crystals of biotite. Vitreous with crystallites, 

 chiefly longulites, gathered together into long thin, distant, parallel 

 bands; so closely are they crowded that the texture almost 

 becomes crystallitic. The rest of the glass is remarkably free from 



Professor Thomas has described a similar obsidia „ -, 



Mr. Cussen from Ngaruahoe, and probably my specimens have the 

 same origin. Thomas, Trans. N.Z. Institute, Vol. xx., p. 311. 



Lake RotoiH, Tauranya Co.— A black vitreous volcanic bomb, 

 highly vesicular inside, and with a thin cracked vitreous skin on 

 the outside. Section of interior portion : clear glass with abundant 

 niargarites and longulites, straight or curved, generally lying 

 parallel and shewing fluxion, but in places confused ; containing 

 occasionally microlites, or small fragments of crystals of felspar. 

 From jNlt. Haroharo. 



Devitrified obsidians and pitchstones, with felsitic texture. 



Mataiira District, Southland — Variously coloured, compact, 

 hard rocks, pink, white, grey, gr 

 scened, sometimes spherulitic. 

 Felsiiic texture, some shew a mc 

 minute, others shew no mosaic. Some have dark markings 

 resembling perlitic cracks. Veins and infiltrations of chalcedony 

 Spherulitic Felsite. 



Light grey rocks with spherulites up to a quarter of an inch in 

 diameter. With crossed nicols shews a very fine mosaic. The 

 spherulites have an opaque white centre surrounded by a broad 

 dark brownish-grey ring and without an outer transparent zone. 

 Another specimen has numerous small spherulites without any 

 ring and shewing an interference cross, in a ground-mass which 

 shews occasionally a large mosaic. Occur as pebbles at Waipapa 

 Point, near the mouth of the Mataura River. Hutton, Trans. N 

 Z. Institute, Vol. xx., p. 269 (Rhyolite). 



