262 W. R. BROWNE AND W. A. GREIG. 
crystals so as to produce typical monzonitic fabric. It is,. 
like the quartz, always interstitial. The relations between 
these two minerals are hard to determine, since wherever 
a boundary between them occurs it is generally of non- 
committal character, but in one slide a small patch of 
micrographic intergrowth between the two was observed. 
The pyroxenes present are of two kinds: in addition to 
augite there is another type, also apparently monoclinic, 
which is possibly clino-hypersthene. These two are very 
intimately associated and are similar in habit, occurring in 
grains or in subidiomorphic stoutish prisms, in places up to- 
3 mm. long but usually smaller. The minerals are much 
cracked, and both commonly show peripheral alteration to: 
hornblende. 
Parallel growths and intergrowths are common, the- 
latter being:sometimes rudely graphic, and the two minerals 
may be clotted or aggregated in glomeroporphyritic fashion, 
although strictly speaking there is no porphyritic fabric 
present. Where parallel growths occur the augite is. 
usually enclosed in clino-hypersthene, indicating that it 
was the first of the two to separate from the magma.. 
Occasional graphic intergrowths of two augite individuals 
in different orientations are to be seen. 
The augite is of a greenish-grey colour in sections about. 
°04 mm. thick. It frequently exhibits repeated orthopina- 
coidal twinning, the lamella being sometimes irregularly 
bounded in part as if through interpenetration, and traces. 
of basal striation and herring-bone structure show up in 
little patches where the mineral is slightly altered. Occas- 
ional traces of the pinacoidal (diallagic) striation are seen, 
but they are not common. Extinction angles up to 43° 
have been measured, and the double refraction is about °025- 
and of positive sign. The optic axial angle is smaller than 
usual, a Series of measurements, kindly made by Miss Ida. 

