608 THE GEOLOGY OF THE WARRUMBUNGLE MOUNTAINS, 



2. Texture : liolocrvstalline, very uneven-grained, porphyritic 

 with large phaneric phenocrj'sts, and with pilotaxitic base. 



3. Composition : the plagioclase consists of phenocrysts of acid 

 labradorite idiomorphic in outline and idiomorphic albite pheno- 

 crysts with corroded edges and numerous inclusions. Amongst 

 the inclusions the most abundant are of augite, magnetite and 

 olivine, but muscovite and quartz fragments also occur. The 

 latter are evidently of extraneous origin. The second generation 

 of felspar consists of prismatic needles of clear albite and an- 

 orthoclase. Many of the phenocrysts show Schiller structure, 

 and zoning is very frequent, the outer portions of a crystal being 

 the more acid. The augite is of two generations, the first being 

 diallagic. The olivine is also of two generations. The most 

 abundant iron ore is magnetite, which occurs chiefly in the base. 

 Apatite is also present. A mineral of the sodalite group occurs 

 interstitially. Less important are the following : — orthoclase 

 phenocrysts in rare fragments; quartz fragments included in the 

 felspar phenoTysts; talc included in labradorite, especially in the 

 crystals showing Schiller structure, and rare flakes of muscovite 

 Avhich may be either primary inclusions or secondary developed 

 by alteration. All these minerals are xenocrysts. 



4. Order of consolidation : 



1. Olivine 



2. Felspar phenocrysts 



3. Diallage , 



4. Apatite ■ 



5. Magnetite 



6. Augite (2nd generation) 



7. Albite (2nd gen. felspar) 



8. Isotropic sodalite or analcite (interstitial) 



Remarks : the augite of the first generation is a titaniferous 



(reddish) diallage, whereas that of the second generation is a light 

 green or colourless diopside. Round the corroded felspar pheno- 

 crysts of the first generation there is frequently a deposit of laths 

 of acid felspar arranged parallel to the original crystal. This 

 deposit frequently encloses magnetite grains. 



