72 



Notes on the Graphitic Slates and asso- 

 ciated Rocks in the Kalgoorlie District. 



By H. B. Corbin, B.Sc. 



(Communicated by Professor Tate.) 



[Read June 7, 1S98.] 



On November 12, 1897, at a meeting of the Boulder Literary 

 and Debating Society, Mr. Bethune read a paper on " Evidences 

 of a Deep Level in the Kalgoorlie District," and therein 

 expressed the opinion that certain graphitic slates in the Boulder 

 North Extended mine at 240 ft. were the result of a filling-in of 

 a cavity by alluvial deposits, and that subsequent lateral pressure 

 had given the alluvial detritus a laminated structure. 



I could not agree with him on the evidence adduced, and as a 

 result of my criticism elicited that he had discovered certain 

 fossils in these beds, which he regarded as conclusive evidence in 

 support of his theory. 



I subsequently in company with Mr. Bethune visited the mine 

 and saw the only section available, and in this communication I 

 propose to describe the geological features which are visible, and 

 to discuss the nature and origin of the so-called fossils. 



The shaft of the Boulder North Extended being close -timbered 

 all the way, and the only open ground available for inspection 

 beincy in the east and north crosscuts, I have had to rely a good 

 deal on hearsay evidence for certain data. 



Virtually, the whole of the way after the surface alluvium (by 

 the miners called "made ground") had been passed through, the 

 shaft was sunk in pink and white clay slates. At about 80 feet 

 water was met with, and at 200 feet crosscuts were opened out 

 N.E. and S.W., that is, at right angles to the general strike of 

 the auriferous lodes in the Kalgoorlie district. 



The west crosscut passed through about 12 feet of fairly hard 

 clay-slates, almost vertical but with a slight underlay to the west. 

 Several veins of ferruginous quartz were cut in the clay-slates ; 

 then a mass of decomposed rock was entered (which from its 

 general appearance, kaolinitic nature and presence of "soapy 

 heads " I take to be a porphyry) and continued to the head of 

 the cross-cut at 50 feet, being occasionally traversed by vertical 

 clay-slates, though not so defined as near the shaft. 



On the east side, the foot wall of the clay-slates is noticed at 

 about four or five feet in from the sliaft, giving a total width of 



