GEOLOG? OF THE JENOLA.N CAVES DISTRICT. 



365 



Norm. 





Per cent. 



Per cent. 



Quartz 



... 6-00 



Magnetite ... 3-02 



Orthoclase 



... 8-90 



Ilrnenite ... 0-91 



Albite 



... 15-20 



Apatite ... 0-67 



Anorthite 



... 20-57 



H0 2 , 0O 2 etc. 3-20 



Diopside 



... 28-61 







Hypersthene 



... 13-32 



100-40 



Class III. 



Salfemane. 



Rang 3. Carnptonase. 



Order 5. 



Gallare. 



Sub-rang 4. Camptonose. 



Magmatic name Camptonose. 



The high percentage of quartz in the norm would be 

 accounted for in large part, if not entirely, by the amount 

 of secondary silica present. The diopside and hypersthene 

 molecules together with a portion of those allotted to 

 anorthite would be combined to form the augite present, 

 and thus give a good idea of the high percentage of that 

 mineral. 



Bearing in mind that a portion of the anorthite should 

 be transferred to form the pyroxene, the average plagio- 

 clase felspar would probably approach a basic andesine or 

 an acid labradorite. The amount of orthoclase present 

 would be small. The fact that the felspars have undergone 

 a good deal of alteration, resulting probably in a loss of 

 some lime, should be taken into consideration when trying 

 to arrive at the actual mineral constitution from the norm. 



In taking a sample of this rock for analysis, fragments 

 as free as possible from the secondary minerals were chosen, 

 therefore the amount of these present, as shown in sections, 

 would probably be more than indicated by the analysis. 



(c) Augite Lamprophyre. 

 From McEwan's Creek, Locality A. 

 Megascopic Description. — A dark green aphanitic rock 

 with numerous fresh looking augite phenocrysts. Small 



