332 l^ROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 



small crystals of green biotite. The quartz phenocrysts are 

 from 1-3 mm. in diameter and occur as allotriomorphic and 

 rounded crystals, frequently fractured and containing 

 numerous dust-like inclusions. In addition to these there 

 are other small inclusions of biotite and larger ones of 

 orthoclase and plagioclase. In one quartz crystal is enclosed 

 an aggregate of quartz and felspar closel}^ resembling the 

 ground mass, but this may be the infilling of a deep embay- 

 ment. Orthoclase occurs as hypidiomorphic phenocrysts 

 which are considerably altered. These often include patches 

 of another felspar intergrown in perthitic fashion. The 

 plagioclase phenocrysts prove to be Albite-Oligoclases, and 

 occur as large hypidiomorphic crystals which exhibit twin- 

 ning on both the Carlsbad and Albite laws. Biotite occurs 

 as browTiish-green phenocrysts which become reddish-brown 

 on alteration, and which show the characteristic strong 

 absorption and perfect cleavage. Inclusions of zircon and 

 apatite are sometimes found. Magnetite occurs in idio- 

 morphic crystals and a few needles of Apatite are present. 

 Zircon is present in small amount. 



Order of consolidation of phenocrysts. — Normal. 



In the ground mass quartz and orthoclase solidified at 

 -approximately the same time. 



Name. — Granite Porphyry. 



Note. — Among the many recommendations embodied 

 in the "Report of the Committee on British Petrographic 

 Nomenclature" is one that "The name granite-porphyry 

 is ambiguous, and should not be used." This name has 

 found considerable use in Australian petrographic litera- 

 ture, where it has a (piite-definite meaning. The rock 

 described above is so like many other Australian so-called 

 "Granite-porphyries" that, principally for purposes of 

 correlation, the author has deemed it wise to retain the 

 term. 



(G.2) 150. {G.4) 152. 



These two specimens also come from the southern part 

 of the Enoggera area. They are very like the rock described 

 above in most respects, but there is seen in these slides a 

 definite tendency for the felspar phenocrysts to be closely 

 grouped together. 



