GEOLOGY AND PETROLOGY OP ENOGGERA GRANITE. 133 



{G.8) 156. 



This specimen comes from the N.N.E. portion of the 

 main Enoggera outcrop. 



Megascopic. — A pink medium-grained rock made up of 

 colourless quartz, pink orthoclase and white plagioelase, 

 together with a little green mica. 



Microscopic. — -Holocrystalline rock of medium and 

 fairly even grain. Quartz occurs in allotriomorphic crystals 

 from 1-1 mm. in diameter. It is fresh, shows radiating 

 fractures, and contains numerous large inclusions of felspar 

 and many dust-like inclusions. Orthoclase is present 

 generally in somewhat altered crystals, from 2-4 mm., 

 showing Carlsbad twinning. Inclusions of both plagioclase 

 and biotite occur. The Plagioclase felspar is a somewhat 

 acid andesine. It occurs in smaller crystals than the ortho- 

 clase, and shows both Carlsbad and Albite twinning, 

 Microeline is also present showing the characteristic combi- 

 nation of Albite and Pericline twinning. Biotite occurs 

 as a few comparatively small dark green crystals which are 

 partly altered to chlorite and contain a few inclusions of 

 apatite. Mag)ietite is present in small amount and shows 

 in places alteration to Limonite. 



Order of consolidation. — Normal. 



Xanie. — Biotite Granite. 



(0.9) 157. 



This specimen comes from X.N.W. part of the Enoggera 

 area. 



Megascopic. — A medium-grained pink rock made up of 

 colourless quartz, pink orthoclase, cream plagioclases, and a 

 dark mica. 



Microscopic. — Holocrystalline, medium grained. 

 Quartz occurs as numerous allotriomorphic and interstital 

 crystals from 1-3 mm. in diameter, considerably fractured, 

 with inclusions of plagioclase, orthoclase, biotite, and apa- 

 tite, and numerous small dust-like inclusions. Quartz also 

 •occurs intergrown with orthoclase and rarely as inclusions 

 in orthoclase crystals. Orthoclase occurs in hypidiomorphic 

 and allotriomorphic crystals from 1-3 mm. in diameter. 

 It usually shows some alteration to sericite or other micace- 

 ous products. It is sometimes intergrown with quartz and 



