ON THE GEOLOGY OF WEST MORETON, QUEENSLAND. 151 



grainsize of the rock is even, about 1 mm., though indi- 

 vidual crystals rise to about 2 mm. in length. The plagio- 

 clase is subidiomorphic in form and includes the largest 

 crystals in the rock. It is twinned on the albite law and 

 occasionally on the Carlsbad law as well. Here and there 

 a little pericline twinning is developed also. The compo- 

 sition is that of an acid labradorite. There is also abundant 

 felspar quite allotriomorphic, untwinned or very hazily 

 twinned, with refractive index less than, or equal to that 

 of Canada balsam, and less than that of quartz. This 

 appears to be anorthoclase. It is granophyrically inter- 

 grown with quartz. In some instances there is a large 

 grain of the felspar with a fringe of granophyre ; in others 

 the granophyric structure extends to the centre of the 

 crystal; while in others there is a nucleus of quartz with 

 a fringe of granophyre, but this last arrangement is not 

 common. Some independent grains of quartz occur, but 

 this mineral is mostly intergrown with anorthoclase as 

 above described. 



The arrangement of the ilmenite is one of the most 

 remarkable features of the slide. It is abundant in thick 

 tabular sections, sometimes simple, sometimes intergrown 

 with the ferromagnesian mineral, and sometimes forming a 

 perfect granophyric intergroivth ivitli quarts and felspar. 

 The ferromagnesian mineral (probably augite) is completely 

 altered, and is represented by an aggregate of fibrous 

 uralite, dark green and pleochroic. Apatite is fairly 

 abundant in thin needles. Order of consolidation : — 



Apatite — _ 



Ilmenite 



Augite 



Plagioclase 



Anorthoclase 



Quartz __ _ 



