BY H. C. RICHARDS. 



103 



the stones used in the base-course under the recently-laid 

 foundation stone of the proposed new Town Hall shoAv 

 a very pronounced acid \ein through them. For biulding- 

 stone purposes the presence of pyrites and its sub- 

 sequent oxidation will always be a grave objection 

 to this stone, but this difficulty could be overcome by 

 opening up stone in those portions of the granite free 

 from pyrites. The Enoggera granite mass is extremelv 

 Variable* and this is shown not only in the nature and relative 

 proportions of the minerals but also in the size of the grains 

 and the fabric of the rocks. Bryan records the granite 

 mass as being made up of two main types, the juajor portion 

 being a iniiform flesh-coloured granite made up of quartz, 

 pink orthoc'ase, })lagio?lase and black-mica phenocrysts 

 set in a fine-grained flesh-coloured groundnuxss ; this type 

 is usually free from ])yritcs. The other type is charac- 

 terised by the rock which has I)een worked at the quariies 

 and it has a greater pro2)ortion of hornblende cvnd biotite, 

 is lacking in pink oithoclase and contains a marked (luan- 

 tiiy of ])yiiles. 



Fi"-. U. ExccLTTivE BuiLDixo. Brisbane. 



View from Ayi'ljani iSlrfct. Erected 1901-.") of saiidstone from Hilidou 

 and Yan Gau on base of aUemate layers of Enoggera and I\It. Crosby 

 granites. 



* Bryan, W. H., Proc. Roy. Hoc. Q'land, xxvi., 1914, p. J48. 



