124 BUILDING STONES OF QUEENSLAND. 



two sand grains in contact with one another (see micro- 

 photograph 1, plate VIII). The brown colouration of the 

 stone is due to the bro\\7i staining of the cementing medium 

 by limonite, also to the occurrence of small patches of this 

 mineral. Its sand grains are angular to subangular and show 

 very little sign of having been transported far. The grains 

 are roughly equidimensional and of even size. The a\erage 

 grain-size is .25 mm. 



The microscopic in\ estigation shows how largeh' the 

 stone is made up of cement, and it is easily understood how 

 the stone is \ery readily worked, also how it is unable ta 

 stand in moist situations. 



All the stone in the quarries is not stained brown, 

 "white stone occurring also. The stone is of \ariable 

 character and needs very careful selection. It works 

 freeh- and \ery easily OA^dng to the large amount of cement- 

 ing medium. It takes a sharp arris and if kept dry, owing 

 to the kindh' climate of south-eastern Queensland, it gi\es 

 ve'y fair weathering results. 



The stone has a Avarm Ijrown appearance and shows 

 very abundant concentric iron-banding and in some cases 

 numerous, small, brown patches of limonite about the size 

 of a pin's head. These iron bandings and the variation 

 in the iron contents in the different stones gi\e a structure 

 of this material a very handsome appearance and warm 

 in conij)arison with the cold, harsh appearance of the white 

 sandstone. It wears freshly, and possesses a very clean 

 appearance. A comparison of the Executive Building wdth 

 the Treasury' building well illustrates these points. 



Very man}' tests have been carried out from time to 

 time. Its specific gravity ranges from 2.26 to 2.42 with an 

 average of 2.34 for seven determinations. This gives an 

 average weight of 146]bs. per cubic foot. The absorption 

 in percentage of dry weight ranged from 2.8 to 4.8 over 

 nine determinations with an average of 3.96. The resist- 

 ance to crushing on twenty-one tests ranges between 2,250 

 lbs. and 8,3811bs. per sq. inch, with an average of approxi- 

 mately 4,7001bs. per sq. inch. 



The brown stone from Wrights Quarry was first used 

 in Brisbane in the Countess Street railwaj- bridge in 1896- 

 The stone was not well selected and is under rather severe 



