PLATE TX. 



7. Olivine Basalt from Municipal Quarry, Toowoomba. The lath- 

 shaped crystals of plagioclase felspar and the rounded granules 

 of olivine are clearly seen. 



S. Rhyolite Tuff from Leichhardt Street Quarry, Spring Hill, Brisbane. 

 The fine-grained nature of the stone, the curved particles of 

 devitrified glass and the phenocrysts of quartz and felspar are 

 seen. 



^. Rhyolite from f'ouncil Quarry, Glen Rock, Esk, showing the fine, 

 even-=,rained nature of the small crystals A quartz and felspar. 



10. " Trachyte " from Mt. Ngun Ngun, Glass House Mountains. The 



lath-shaped crystals of sanidine felspar and the dark crystals 

 of soda-rich augite are seen clearly. 



11. " Trachyte " from Mt. Tibrogargan, Glass House Mountains, showing 



a phenocryst of sanidine felspar set in a very fine-grained 

 groundmass of sanidine and soda-rich augite crystals ; the 

 latter are arranged in lines and patches. 



12. Sandstone from Petrie's Breakfast Creek Quarry, Albion. The 



coarse nature of the sand grains and the abundant cement are 

 seen. 



I 



