82 

 Complete Analysis of the mount Gambier Basalt, 



WITH PETROGRAPHICAL DESCRIPTIONS. 



By Evan R. Stanley, Student of the University of Adelaide. 

 (Communicated by W. Howcliin, F.G.S.) 



[Read May 4, 1909.] 



Plate II. 





Contents. 



I'AUK. 



I. 



Introduction ... 



... 82 



II. 



Vesicular Olivine Basalt 



... 83 



III. 



Chemical Composition 



... 86 



IV. 



Slaggy and Vitrophyric Types of Lava 



... 91 



V. 



Vesicular Vitrophyric Olivine Basalt 



... 92 



VI. 



Vesicular Olivine Basalt (slaggy type) 



... 93 



VII. 



Vesicular Basalt 



... 95 



VIII. 



Lherzolite 



... 96 



IX. 



Remarks 



... lOU 



X. 



Conclusion 



... 100 





Explanation of Plate 



... 100 



I. — Introduction. 



Mount Gambier is situated in the South-Eastern por- 

 tion of South Australia, in the Hundred of Blanche, about 

 305 miles from Adelaide by rail. The township is about 140 

 ft. above sea-level, but Mount Gambier proper is about 600 

 ft. higher, and is situated south of the town. It includes 

 four distinct lakes, namely, the Blue Lake, Leg-of-Mutton 

 Lake, Valley Lake, and Brown Lake, the latt«r probably 

 being the site of the crater. 



This paper, which represents the first of a series, has 

 been written with the object of describing certain typical 

 volcanic rocks occurring at Mount Gambier. 



The geology of the South-East, including Mount Gam- 

 bier, has been described and published by the Rev. J. E. 

 Woods in his "Geological Observations in South Australia," 

 1862. 



Professor R. Tate refers to the South-Eastern district of 

 South Australia in his presidential address before the Philo- 

 sophical Society of Adelaide in 1879. 



H. Y. L. Brown, (-) Government Geologist of South Aus- 

 tralia, reports on the temperature, depth, and geology of 

 the principal lakes in the Mount Gambier district. 



(1) Parliamentary Papers, South Australia, 1883-4. No. 256. 



