402 



H. G. FOXALL. 



The OCCURRENCE of ISOLATED AUGITE CRYSTALS 



at the TOP of the PERMO-OARBONIFEROUS 



UPPER MARINE MUDSTONES at 



GERRINGONG, N. S. WALES. 



By H. G. Foxall. (Communicated by Prof. T. W. E. 

 David, b.a., f.g.s., f.r.s.) 



[Read before the Royal Society of N. S. Wales, November 16, 1904.~\ 



These crystals occur iu great numbers embedded in a 

 matrix of tuffaceous mudstone about half a mile south of 

 Black Head, Gerringong. A few crystals also occur in a 

 similar formation to the north of Black Head, but they are 

 not so numerous there. In the former locality the crystals 

 arc found right on the shore-line, most of the specimens 

 collected being found actually below high- water mark. 

 They are very perfect and evenly developed, and can be 

 picked out clean from the matrix, In many cases they are 

 twinned on the 100 face. 



At the suggestion of Professor David, crystallographical 

 and chemical examinations were made of these crystals in 

 the Geological and Chemical Laboratories, respectively, of 

 the University of Sydney. The results are given below, as 



