142 F. W, BUTTON. 



alteration products. Fluxion very apparent. The porphyritic 

 minerals are plagioclase, augite, hornblende, olivine (altered) and 

 magnetite. The plagioclase crystals go to -13 in length. The 

 augite is greenish-brown, not abundant, idiomorphic, up to -06 in 

 length, slightly pleochroic when in thick sections. The hornblende 

 is rare, dark brown, in long broken prisms. The olivine is altered 

 into a dark brownish-red translucent mineral, probably hfematite. 

 There is also occasionally a colourless aggregate. Hoon Hay 

 Quarry, above Governor's Bay. Several of the bridges over the 

 Avon are built with this stone. 



2. A dark grey rock thickly crowded with white felspars, up to 

 •30 m length, the other porphyritic minerals not conspicuous. 

 S.G. 2-81. Section: Ground-mass moderate or small, crystallitic, 

 crowded with felspar microlites, the isotropic portion generally 

 opaque with longulites and containing rather large grains of mag- 

 netite in abundance. The porphyritic minerals are plagioclase, 

 augite, and olivine (altered). The augite goes up to -03. The 

 olivine is altered into a red translucent hematite. Secondary 

 haematite surrounds the magnetites. Port Hills. Used in build- 

 ing Canterbury College and parts of the Museum in Christchurch. 



In other specimens of the same kind of rock from the Sumner 

 and Lyttelton road, some of the olivine is unaltered. 



3. Grey compact rocks with scattered felspars and augites. 

 S.G. 2-66 to 2-69. Section : Ground-mass abundant, vitreous or 

 microlitic with abundant felspar microlites, and scattered mag- 

 netite grains. The porphyritic minerals are plagioclase, augite, 

 and olivine. The plagioclase goes to -10, often not abundant. 

 The augite is pale greenish-brown, up to -03. The olivine ie 

 colourless, up to -03 ; sometimes altered to red-brown translucent 

 haematite. Heathcote and Sumner Road, in several places. 



3fount Egmont.~A grey rock with small felspars and conspicu- 

 ous black pyroxenes. S.G. 2-84. Section : Ground-mass moderate, 

 crystallitic, longulitic, thickly strewn with microlites of felspar 

 and grains of magnetite. The porphyritic minerals are plagioclase, 

 augite, olivine, and magnetite. The plagioclase is abundant but 

 small, up to -04 but generally less, squarish or in laths. The 

 augite is in large yellow-green crystals up to "08 in length. The 

 olivine is colourless, scarce, up to -05 in length. From the northern 

 slopes of the mountain. 



Chloritic Andesite. 



The whole of the bisilicates changed into hydrous unisilicates. 



Nelson District.—l. A dull pale green rock, compact and 

 homogeneous except occasional black patches. S.G. 2-86. Section : 

 Ground-mass very abundant, crystallitic, partly felsitic, colourless 

 but full of chloritic infiltrations and specks of leucoxene. The 



