198 VOLCANIC ROCKS OF SPBINGSURB. 



characters. As these volcaiiic rocks are almost certainly 

 of Cainozoic age, a similar age might with confidence be 

 iissigned to the volcanic rocks of the Springsure district. 



PLATE XII. 

 Figures 1-6 magnified 22 diameters. 



1. Phonolite from Virgin Rock, the Mountain, Springsure. The granule 



of nosean in the centre of the field and crystals of anorthoclase are 

 seen set in a groundmass of felspar and nosean. 



2. Same section as above but under crossed nicols. The isotropic 



character of the nosean is well shown. 



3. Trachyte from Opal Ridge, under crossed nicols. It shows perlitic 



cracks in one portion and the edge of a large spherulite in the other 

 portion. 



4. Glassy Basalt from Opal Ridge, under crossed nicolS. The scoriaceous 



character is well shown, also the glassy nature of the base. The 

 tridymite lining the cavities is not observable in the microsection. 



5. Fayalite Basalt from upper flow, Mt. Boorambool. Composed of 



plagioclase, fayalite, augite and iron ores. The rounded granules 

 with the dark borders are fayalite crystals. 



6. Basalt from Scott's Well, Springsure, composed of plagioclase, augite 



and the iron ores. 



