200 BUILDING STONES OF ST. JOHn's CATHEDRAL, BRISBANE 



The igneous rocks, namely the Granite and Basalt, 

 have been used in the basement ; the main structure is of 

 the Brisbane tuff, which is generally called " porphyry," 

 while the sandstone used outside comes from Pyrmont, 

 Sydney ; the inside sandstone being obtained from 

 Helidon. 



Description and Some Tests of the Stones. 



(1) TUFF. 



This is the material familiar to everybody, and which 

 is used for road-metal, coping-stones, pitchers, building 

 material, etc. It is a fine-grained frag mental rock formed 

 by the consolidation of volcanic detritus such as ashes, 

 sand and lapilli. It is a hard compact material, exhibiting 

 a variety of colours, salmon, pink, grey, white, green, 

 purple, etc., which blend well with one another. The 

 colour effects may be well seen on roads built of this 

 material, after a heavy downpour of rain, when a handsome 

 multi-coloured mosaic is produced. Owing to the nature 

 of its texture it does not take a polish, and in the Cathedral 

 is used in medium-sized blocks, either rock-faced or smooth- 

 dressed. It is interesting to note that while tuffs are not 

 generally used for building purposes owing to their porosity 

 and friability, the so-called '' peperino " of the campagna 

 of Rome and Naples is a tuff, and has been used in other 

 buildings in those cities, it was also used in the houses of 

 Herculaneum and Pompeii.* 



The material in question was obtained from the 

 O'Connelltown quarries, one of the numerous tuff quarries 

 in the immediate neighbourhood of this city. Immense 

 quantities of this excellent material exist, as it occurs 

 bedded up to a great thickness, as shown opposite the 

 Botanic Gardens, and at the Leichhardt Street quarry. 

 It occurs geologically almost at the base of the Tria-Jurassic 

 System, being separated from the much- older underlying 

 sohists by a few feet of higlily carbonaceous shales, which, 

 iix many places, contain abundant traces of fossil trees. 

 The source of the ashes which build up this tuff was in all 

 probability an ancient volcano, of which the present 

 Enoggera granite marks the base. 



*Hull, Building and Ornamental Stones. P. 283. 



