206 NATURE, OCCURRENCE, AND ORIGIN OF ALUNOGEN. 



The incrustation which has formed at present is easily 

 removed and as the large flakes are broken away shrinkage 

 cracks are very evident indicating that the deposit gradually 

 becomes less hydrated : this is borne out by the analysis 

 in comparison with the theoretical alunogen analysis. 



The amount of impurity in the incrustation is something 

 over twenty-six per cent, and in order to remove as much as 

 possible of this the s^^ldicate which has been experimenting 

 with the material adopted the following method. The 

 incrustation is crushed and treated with water. Owing to 

 hydrolysis, a flocculent gelatinous mass of aluminium 

 hydrate is formed and the clay and sand impurities are thrown 

 out on the bottom of the containing vessel. The whole 

 is treated with hot water and the aluminium sulphate 

 leached out as completely as pos-sible ; the solution is then 

 evaporated down in a large boiler and the crystalline 

 aluminium sulphate obtained. 



For such i^uri^oses as paper-making, water-clarifi- 

 cation, tanning and dyeing, this material has a good com- 

 mercial value, so that it is of economic importance. 



Owing to its soluble nature, alunogen does not usually 

 occur except in arid areas and as these generally have poor 

 means of communication the material is not a regular 

 commercial article. 



Other Queensland Alum Occurrences. 

 Three occurrences are noted in the Mineral Index* ; 

 in the old workings of the Golden Gate mine, four miles 

 N.W. of Croydon; on clay at the Blair AtholCoal Mines^ 

 near Clermont, and in caves of sandstone at Glen Haughton, 

 35 miles N.W. of Taroom. Another record of considerable 

 interest, is found in the evidence tendered by the Hon. 

 A. C. Gregory to the Parliamentarj^ Select Committee to 

 report on the Sandstone Quarries of the Southern District 

 1888t. Speaking of the Highfields sandstone which was 

 used in the first ^ving of the Treasurj^ Building, Brisbane, 

 the witness said : — " One peculiarity of this stone at this 

 place is that it stands better if it is thoroughly washed by 

 rain than when it is practically covered. The fact is that 



*Q'ld Geol. Surv. Pub. 241, p.9. 

 t Votes and Proc, 1888, iii, p. 1037. 



