TRANSACTIONS OF SECTION C. 141 



Sections. — Clear ground-mass of allotriomorphic nepheliue, 

 not very abundantly intermixed with microlites of sanidine 

 and rather large, light-green ones of £egirine(?). Idiomorphic 

 nephelines large, very clear, not numerous ; some square sec- 

 tions show pronounced parallel cleavage-cracks. Sanidines, 

 partly in Carlsbad twins, numerous, and some very large. They 

 are much cracked, and more or less thickly impregnated with 

 small portions of the ground-mass, dusty matter, green micro- 

 lites, grains of iron-ore, and roundish particles of glass. These 

 inclusions are rarely distributed evenly throughout, but are 

 mostly confined to the centre parts of crystals, leaving clear 

 zones of greater or less width around ; there are also crystals 

 with the centre parts clear and the inclusions forming uneven 

 margins around. One crystal was observed bounded on one 

 side by a jagged rim of w^ater-clear glass. Augite very abundant 

 in large and small columnar crystals, which are, as a rule, more 

 or less abundantly impregnated with grains of iron-ore. Some 

 of the larger crystals are rendered nearly black-opaque by it ; 

 others have broad, black margins, leaving only small clear 

 portions in the centre. They are mostly of fine grass-green 

 colour, but there are some amongst the larger ones which 

 arc light -brown in the centre and green around. Olivine 

 in large irregular grains and crystals, with broad black 

 margins of dusty iron-ore, is rather frequent. Some crystals 

 are thin and long -columnar like those noticed in No. 7. 

 A number of grains occur sometimes closely grouped to- 

 gether. One large grain was observed showing a broad rim 

 of green microlites so closely aggregated as to look like solid 

 augite. Apatite scarce. Iron -ore abundant in large and 

 small grains. 



11. Froyn Cliffs between Purakanui Cliffs and Hayicard's 



Bluff. 



Rock. — Dark greenish-grey, very fine-granular, rendered 

 strongly porphyritic by crystals of feldspar. Contains scat- 

 tered large patches of black hornblende ; but this mineral, as 

 shown in the thin section, is only sparingly distributed in the 

 base of the rock. Gives a fair amount of gelatinous silica on 

 treatment with HCl. 



Sections. — The clear ground-mass is composed of a mixture 

 in about equal proportions of allotriomorphic nepheline and 

 microlites of sanidine, through which are rather scantily dis- 

 tributed the usual pale-green microlites (a3girine?). Idio- 

 morphic nephelines, in the average of small size, are tolerably 

 numerous. Sanidines, some of large size, plentiful, and the 

 large ones are generally full of inclusions of ground-mass, 

 grains of iron-ore, dusty matter, &c., sometimes zonally 



