p. 40 ; Cox, Rep. Geo!. Expl. 1883-4, p. 84. Analyses are give 

 ^'V \V. Skoy, Col. ]\[useuin and Lab. Report, Xo. 7, p. 17 ; an 

 von Htiuer in Gaol. of Canterbury, p. 285(Quartziferous porpliyry 

 -Microscopical examinations have been published bv Daintree^i 

 Tians. N.Z. Inst., Vol. vii., p. 459 (Trachytic Rocks) and Co: 

 Rep. Geol. Exj.l. 1883-4, p. 107. 



1^. A' itreoub texture. (Vitropliyre in j.art.) 

 Jfti/nru IlUh, S,'h'-i/,t Co.- From dark brown and sub-vitreoi 



colour, more or le^s abundant." S.(.i. 2'40 to i-.')2. "lection 



and the ground-nia 

 glah.'ies. 'rhe porph 

 a little plagioclase : 



lliey will be found described under tlie name of Pitchstones ; a 

 name which T limit to non-porphyritic rocks. 



direction, sub-conclioidal in others. S.G. L>'40. Section : Ground- 

 mass very aljundant formed by a brown glass rather closely studded 



cracks which are crossed l>y the margarite-s, and which are narrowly 

 margined by clear brown glass. The porphyritic minerals are 

 quartz, sanidine, plagioclase, and biotite. The quartz is idiomorphic 

 or allotriomorphic about -0 1 in diameter ; the felspars go up to 

 ■<J8. Plagioclase is subordinate to the sanidine. Biotite is rare, 

 goes up to -Ol.-) inch. Haast, Rep. Geol. Expl., 1873-4, p. 11. 

 U 



with distinct plane of divis'i 



and shewing scattered crystals of hornblende 



gonal plates ; tiie grey portion more glassy. 



the naked e 



plagioclase, 



he porphritic minerals a 



I little hornblende, biot: 



•06. The plagioclase is 



ry^ . . a size of -OG. The horn.^.^.xx,^ ..v,. ., — 



■^'>, It IS brown and strongly pleochroic. The biotite is very dark 



quartzes go up to -06. The plagi. 



1,>ne, both reach a size of ■()(). " The hornblende does not 



