510 H. S. JEVONS, H. I. JENSEN, T. G. TAYLOR AND C. A. SUSSMILCH. 



it may be of interest to compare quantitatively the mineral 

 compositions (modes) of the rocks of which the analyses 

 have been quoted above, in cases where these have been 

 calculated. The percentage of the mineral compositions 

 by weight will be found in the subjoined table. The letter 

 c (circa) preceding a figure for any mineral means that 

 it is to be taken as only approximate. It is interesting to 

 note that the minerals, which are of the same character in 

 all the rocks, vary very considerably in their relative pro- 

 portions in spite of the uniformity of chemical composition. 







III. 



V. 



XII. 



VII. 









(Prospect) 





Plagioclase 



... 



53 



36 



38 



45 



Orthoclase 



... 



3 



2 



1 



1 



Augite 



... 



20 



38 



30| 



26 



Olivine ... 



... 



15 



6 



14 



12f 



Biotite ... 



... 



1 



2 



11* 



n 



Iron ores and 



apatite ... 



8 



16 



5 



6 



14. Nomenclature of the Hocks. 



The names which should be used to denote the rocks 

 already described in this paper must now be considered. 

 The appropriate naming of rocks in the segregation veins 

 will be discussed later. The comparison of the Prospect 

 with other rocks, undertaken in the last section, shows that 

 it is impossible to assign unhesitatingly to the former any 

 single name from amongst those in common use. Amongst 

 New South Wales geologists the main mass of the Prospect 

 rock has always been called a dolerite in the sense of Teall, 

 Hatch, and others, and not in the German sense, or a 

 diabase in Harker's sense, or perhaps by some in Bonney's 

 or the German sense of an altered or old fine-grained basic 

 rock, as the stone is green with chloritization. The compact 

 dark bluish rock of the outer envelope has always been 

 spoken of as basalt. For precision the prefix olivine- was 



