BY A. B. WALKOM. 



51 



breaking with a concboidal fracture, in contrast to the more 

 brittle bituminous coal of the Jpswich Beds." 



The Ipswich coals are steam-coals, and are suitable for heatino- 

 and coke-making; the Walloon coals are essentiall}^ gas-coals. A 

 table of typical analyses of the coals from various areas has been 

 published by Mr. Dunstan,* from which we may quote the typical 

 Ipswich and Walloon coals for comparison. 



The most notable point of contrast between the two is in the 

 relation of volatile hydrocarbons to fixed carbon; in the Ipswich 

 coals, the latter is very much in excess of the former, while, in 

 the Walloon coals, the two are of about the same value. In 

 some cases, Walloon coals show a much higher percentage of 

 fixed carbon than of volatile hydrocarbons, and the analysis is 

 then indistinguishable from that of Ipswich coals; in these cases, 

 however, the field-relations of the strata usually supply the ex- 

 planation for this irregularity, by the presence of intrusive rocks 

 not far away, and resultant alteration of the coal. 



In normal cases, then, there is a more or less marked distinc- 

 tion between the coals of the Ipswich and Walloon Series in 

 Queensland, and this distinction is of some practical value in 

 helping to distinguish between the two Series. The Walloon 

 coals are distinctive, and can frequently be recogni.'^ed M'ith a 

 reasonable amount of certainty as belonging to that Series. The 

 Ipswich coals, however, though they are distinct from the Wall- 

 oon coals, are very similar to the coals of the Burrum Series, of 

 Cretaceous age, and their age cannot be identified by the nature 

 of the coal. 



Queensland Geol Surv. , l^ublication No.239, p. 23. 



