144 F. W. HUTTON. 



chroic, changing from yellow-green to blue-green. Apatite occurs 

 in the chlorite pseudomorphs. Other secondary minerals are 

 quartz, magnetite, and leucoxene. S.G. 266 to 273. From 

 Karaka and Waiotahi Creeks. 



3. Ground-mass moderate, crystallitic, Ion gulitic, with numerous 

 felspar microlites and rather large grains of magnetite. Original 

 porphyritic minerals are plagioclase and magnetite. Secondary 

 minerals are chlorite after augite and calcite after hornblende. 

 The plagioclase goes up to -08, it is much decomposed but distinctly 

 zoned. The hornblendes are filled sometimes with chlorite, some- 

 times with calcite and a magnetite wreath. The chlorite in the 

 hornblendes is greenish-brown and slightly pleochroic, that in the 

 augite is blue-green and almost isotropic. S.G. 2'68. Forms a 

 dyke on the shore a little north of Tapu Creek. 



(B) With pseudomorphs after augite only. 



4. Ground-mass abundant or moderate, partly vitreous and 

 partly felsitic, rather opaque with small specks of leucoxene, 

 colourless but with infiltrations of green chlorite. Original por- 

 phyritic minerals are plagioclase and magnetite. Secondary 

 porphyritic minerals are chlorite after augite. Other secondary 

 minerals are quartz, calcite, pyrites, and leucoxene. Apatite 

 occurs in the chlorites. S.G. 2-45 to 259. From Te Aroha and 

 Thames district generally. These rocks form the country in which 

 the auriferous veins are situated. Hutton, Rep. Geol. Expl. 

 1868-9, p. 18 (Trachytic tufa); Hector, I.e., p. 40, Table of 

 Analyses ii. to vi. ; Davis, I.e., 1870.1, p. 56 ; Cox, I.e., 1882, p. 

 4; McKay, I.e., 1885, p. 192. 



(C) With pseudomorphs after augite and enstatite. 

 a. With quartz. 



5. A dark greenish-grey rock, with greenish-white felspars- 

 S.G. 2-70. Section : Ground-mass rather abundant, crystallitic. 



(after augite), bastite (after enstatite) and magnetite. The quartz 

 is rare, in grains -02 or -03 in diameter. The felspars go to 'Ub 

 and the bastite to -03 in length. Waiotahi Creek, 

 b. Without quartz. 

 G. Ground-mass moderate or small, felsitic, with chloritic infil- 

 trations. Original porphyritic minerals are plagioclase, and mag- 

 netite. Secondary minerals are chlorite after augite, and bastite 

 after enstatite. Other secondary minerals are quartz, calcit^ 

 pyrites and leucoxene. The felspars are much decomposed ana 

 sometimes have chloritic infiltrations. The chlorite is blue-green 

 and partly isotropic, partly anisotropic and slightly pleochroic 



