Physiograplnj of Bulla Area. 3 3i 



The rather high CaO content, and the relatively low K^O content, 

 of the Bulla rock favours granodiorite rather than adamellite, and 

 the miscroscopical examination confirms this determination. 



Megascopic Character . — It is a rather coarse grained, grey rock 

 with many crystals, 10 mm. in diameter. Quartz, plagioclase, 

 orthoclase, biotite and a little pyrite can be seen. Ihe quartz has 

 a greasy lustre, and the felspar tends to be greenish. The rock 

 takes a fine polish, though the coarse biotite is inclined to give the 

 surface a chipped appearance. Basic segregations with their 

 rounded outlines are very common. Ibe specific gravity of fresh 

 rock is 2.677, and thus in keeping with its determination as 

 granodiorite. 



Microscopic Character. — It is a non-porphyritic, hypidiomor- 

 phic, holocrystalline rock with crystals of various 'sizes. It is 

 medium to coarse in grain, with a rich assortment of minerals.. 



