1872.] DAINTREE GEOLOGY OF QUEENSLAND, 303 



Silica 61-433 



Alumina 20-293 



Ferric oxide 1-220 



Ferrous oxide 3-260 



Lime 3-233 



Magnesia 1-566 



Potash 1-686 



Soda 6-173 



Water, constitution , 0-725 



Water, hygroscopic 0-300 



Specific gravity 2-712. 99-889 



Mr. AUport's description of this, from a microscopic examination, 

 was : — " That it was an altered porphyrite, with pseudomorphs after 

 felspar, in a granular felsitic hase, and contained minute grains of 

 magnetite, and also a little chlorite." The specimen analyzed did 

 not contain pyrites, but was slightly tinged with carbonate of copper 

 in the mass, a portion not so stained being selected for the deter- 

 mination of the ingredients. 



Rocks of this type, associated with auriferous veins, are developed 

 in the Black Snake " reefing districts," on the flanks of the Berserker 

 Range (PI. XL fig, 3), in New-Zealand Gully, and in other mining- 

 ai'eas near Eockhampton, also within the auriferous radius around 

 Mount Wyatt. 



Group 2. 

 Pyritous Diorite and Diabase. 

 In the chapter on the Palaeozoic rocks, correlated with the Devo- 

 nian of Europe, the analysis of a type specimen of the Gympie crys- 

 talline Diorite is given. That of a diabase tufa, containing organic 

 remains, which forms an interstratified portion of the Devonian 

 series, the one probably representing the core, the other the ejecta, 

 of a Devonian volcano is also given. 



As this group, however, is widely distributed along the eastern por- 

 tions of Queensland, and seems so important an indicator of auriferous 

 Avealth, the analysis of another specimen (PI. X. fig. 3) taken from near 

 the junction of Granite and Twenty-mile Creek, in the Gilbert district, 

 is here given. 



Ultimate Analysis. 



Silica 47-465 



Alumina .- 19-485 



Ferric oxide 1-570 



Ferrous oxide 11-735 



Lime 7-400 



Magnesia 5-670 



Sulphur 0-335 



Potash 0-280 



Soda 2-725 



Carbonic acid 1-461 



Water, constitution 1-150 



Water, hygroscopic , 0-350 



99-626 



