156 VOLCANIC AREA OF EAST MORETON, ETC., DISTRICTS, Q., 



base contains felspar (sanidine); quartz has not been identified in 

 it, but may be present interstitially. The amphiboles present are 

 riebeckite in dendritic (poikilitic) aggregates, and a little brownish 

 hornblende (eossyrite 1), of similar habit. 



Sp. C. Handspecimen like the preceding. This is a 

 noncrystalline, fine-grained rock of trachytic fabric. The 

 constituents are isometric and lath-shaped sanidines, sanidine 

 microlites of the base, interstitial quartz, amygdules of spherulitic 

 chalcedonic quartz, and deep blue, almost black, pleochroic soda- 

 hornblende (variety of riebeckite) in rods. The analysis of this 

 rock (Anal.ii. p. 168) shows it to be a comendite. Magmatie name, 

 " Kallerudose," near " Liparose." 



Sp. D. A noncrystalline, extremely fine-grained rock, with a 

 microgranitic (granular) fabric. 



The constituents recognisable are sanidine, and very fine- 

 grained blue hornblende. 



Sp. E. Handspecimen of a bluish colour, with well marked 

 flow-structure. 



The blue colour appears, under the microscope, to be due to a 

 bluish glass. The rock is hemi-vitreous. Fluxion-structure is 

 very distinct. A considerable amount of secondary quartz is 

 present. 



From the above descriptions it will be seen that the Coolum 

 rocks are fine-grained Riebeckite Comendites, varying from 

 noncrystalline to hemi-vitreous in ci'ystallinity, and from ortho- 

 phyric to trachytic and microgranitic in fabric. 



The comendite from Mt. Cooroora, near Pomona, is, in hand- 

 specimen, like those from Cooran, Coolum and Conowrin. 

 Microscopically, also, it resembles these rocks. Its fabric is 

 orthophyric The amphibole consists of almost opaque blue-black 

 rods, in extremely thin sections pleochroic from blue to greenish- 

 blue (riebeckite). 

 Sp. No.109. Loc: Mt. Pinbarren. 



This specimen is a black rock, light in weight, with a slaggy 

 appearance. 



Examined microscopically it is observed to be hemicrystalline, 

 very fine-grained, and to possess a hyalopilitic fabric. In 



