10 ox HAUYNE-TRACHYTE AND ALLIED ROCKS. 



AuGiTE Syenite. 



Found /// .situ on beach between Regatta Ground and Lymington. 



Ma c) 'osnip ir rli a ) 'actoi \-i . 



Fine-grained, with nnmerous lustrous faces of felspars, 

 and specked ^Yith green augite. Some of the felspars are 

 idiomorphic. Colour of the rock light grey. 



Microscopic cJiaracters. 



Structure, hypidiomorphic-granular, many of the fel- 

 spars strongly idiomorphic parallel to 001 and 010. A 

 few of these much larger than the rest, Avith numerous 

 enclosures of sphene and small felspar crystals. Zoning of 

 felsi)ars quite a feature. Many of the orthoclase felspars 

 are glassy, and have a sanidine habit. There is a good deal 

 of albite-twinned felspar and microperthitic intergrowth of 

 albite-oligoclase with orthoclase, some of the twinning 

 being extremely fine, and cross-twinning is well shown. 

 The extinction angles yielded by different crystals seem to 

 be those of both albite and oligoclase. 



A pale green augite (malacolite) is frequent. Its pleo- 

 chroism is very slight. Its extinction angle in the prism 

 zone is as high as 11°. Wedge-shaped crystals and grains 

 of sphene plentiful. A little idiomorphic apatite and 

 interstitial quartz. We have not noticed any garnet in 

 this syenite. 



Hauy^xe Aplite. 



Sp. gr. 2* 75. 

 Found at Port Cygnet, but the precise locality is unknown, 



Macroscoj)ical cJiaracters. 



A medium-grained dark grey rock, consisting largely of 

 small columnar and tabular sanidine crystals,, some of 

 which exceed the rest in size. A parallel arrangement of 

 felspars occurs, but is inconstant, the crystals lying mostly 

 in all azimuths. With a hand-magnifier, granular augite 

 seems plentiful, and crystals of yellow sphene are seen 

 here and there. Small grey and white spots represent 

 nosean, but this mineral can only be identified micro- 

 scopically. 



Jlicruscopicd I clifiractrrs. 



The rock is seen to be essentially composed of sanidine, 

 augite, and nosean, with the minerals sphene, apatite, and 

 zircon as accessories. The sanidine is clear, and mostly in 

 columnar forms, with Carlsbad twinning. Some of these 



