3-04. Section : Ground-mass abundant, between microgranitic 

 and microlitic ; formed by plagioclase laths, -005 in length, crystals 

 of brown hornblende, -003 to 004 in length, crystals of pink 

 augite, -003 and upwards, and grains of magnetite ; the plagioclase 

 being quite subordinate. In addition to these minerals there are 

 a number of colourless needles often arranged parallel to each 

 other, which penetrate tlie felspar laths; probably they are either 

 Wollastonite or else Tremolite. The porphyritic minerals are 

 olivine and augite. The olivine is not very abundant, and mostly 

 changed to serpentine ; when fresh it is of a pinkish-olive colour ; 

 It goes up to -08 in length. The augite is idiomorphic, and purplish 

 in colour, lighter in the middle and with a broad peripheral zone 

 darker ; not pleochroic ; in size up to -06 in length but intermediate 

 sizes occur connecting the porphyritic augite with tliat of the 

 Forms a dyke in Granite, two miles from Lyell, on 

 J TT . , rx, -^2. Inst., Vol. XXII. 



Augite Dolerite. 

 Spriuf/Jleld, SeJwyn Co.— A dark brownish-grey rock, without 

 porphyritic minerals. S.G. 2-88. Section: Granular ; composed 

 or plagioclase, augite and magnetite. Secondary minerals are 



i:» luatite, liiuonite, and a brown decomposition product with 

 ^^'^^ni^^ate polarization. The plagioclase is in laths, from -02 to 

 ■"■I la length, and with extinction angles between the lamellae up 

 to 40\; it is therefore probably anorthite. The augite is brownish- 

 green, chieHy allotriomorpliic, from -02 to -06 in diameter, 

 occasionally twinned, in places semi-ophitic. The magnetite is in 

 considerable quantity but largely decomposed into limonite. Forms 

 a small hill near the Railway Station. Haast, Rep, Geol. Expl., 

 l^^'l-2, p. 26 {Kowai Corner) ; Geol. Cant. p. 300. 

 Olivine Dolerite. 

 Oamaru Cape, Waitaki Co.— Compact greyish-black rocks with- 

 out porphyritic minerals. S.G. 2-80. Section : Granular, com- 

 posed of plagioclase, augite, olivine (altered) and ilmenite, with 

 perhaps a little opaque base. The plagioclase is in laths -03 in 



ength. The augite is either in grains -62 in diameter or in prisms 



^•^ X -001, and collected into bundles ; it is purplish and slightly 

 pleochroic, granulitic. Secondary minerals are chlorite and 

 terpentine after olivine. Hutton, Trans. N.Z. Inst.Vol.xix.,p.417. 

 Mot^rakx Peninsula. — A yellowish-grey compact rock without 

 porphyritic minerals. S.G. 2-88. Section : Ground-mass abundant 



omposed of plagioclase, augite, olivine (altered) and ilmenite. 



.^he plagioclase is in laths, from -01 to -04 in length. The augite 



pale greenish-yellow, in grains from -003 to -01 in diameter, 



«en gregaritic, the clusters up to -08 in diameter. The only 

 porphyritic mineral is olivine whioli is altered into a green non- 



