Vol.69.] TETKOLOGY OF THE ICALGOOELIE GOLDFIET.D. 67$ 



Ancient sediments. A : — Figs. 1-3. 



B :— Pis. X-XII ; XIV, fig. 1. 

 Fine-grained aniphibolites. A :— Figs. •>, 6, 10, & 42. 

 Fine-grained greenstone (with chloritoid). A : — Fig. 47 (' Ottvelite-schist '), 

 Calc-schists. B : -PI. XIV, fig. 2 ; PI. XVIII. (' Metamp'rphic tuffs.') 

 Serpentine. A :— Fig. 48. 

 Pyroxenile (amphibolite). A : — Fig. S. 

 Quartz-dolerite-greenstones and bleached greenstones. 

 A :— Figs. 7, 33, & 34. 



B :— Pis. XIX-XXV ; LXII-LXIV. (f Quartz-andesite. 

 gfanophyric dacite, aphanitc.') 

 Lode-matter in the quartz-dolerite-greenstones. 

 A :— Figs. 26, 27, & 32. 

 B :-Pls. L, LI, & LXI. 

 Porphyrites. A : — Figs. 11 & 13. 

 Albite-porphyries. A : — Fig. 14. 



B :— PI. XXVIII. 

 Jaspers and graphitic schists. A: — Fig. 17. 



B :— Pis. XXV 1 1 & XXVIII. 



In the Bulletin above cited, Mr. Gibson amplifies his previous- 

 account of the geology of Kalgoorlie by describing the chief rock- 

 types in some detail. Mr. Simpson also adds further details of the 

 petrography in an account of the minerals found in the field, and 

 discusses the alterations of the rocks in a chapter dealing with 

 the ores. Several new analyses by Mr. Bowley are included in the 

 Bulletin. 



While the classification of the individual rocks adopted by 

 Mr. Gibson is substantially the same as that given in this paper, 

 the treatment of their relationships is in reality fundamentally 

 different. Neither Mr. Gibson nor Mr. Simpson has recognized 

 the albitization of the quartz-dolerites and porphyrites, or the close 

 connexion between this alteration and the intrusion of the por- 

 phyrites and porphyries. This leads the first-named writer to state 

 that the porphyrites are of no economic importance ; whereas the 

 discovery of porphyrites or albite-porphyries outside the Kalgoorlie 

 area should be of great value to the prospector, as indicating an area 

 of possible albitization with a heightened possibility of discovering 

 telluride-lodes. So far from recognizing the albitization, Mr. Gibson 

 states that the felspars of the greenstones are frequently . saus- 

 suritized : an assertion that is in practical contradiction to his 

 statement that epidote is rare, and when present is associated with 

 chlorite. 



Mr. Simpson, in discussing the alterations that have given rise to 

 the ores and the wall-rocks of the lodes, still adheres to his pre- 

 viously expressed conclusion that the coarse greenstones have passed 

 through an amphibolitic stage, without, apparently, considering 

 the possibility of their direct derivation from the original rock, or 

 recognizing that the rocks from which they were derived were r 

 on the whole, more siliceous than those now represented by 

 amphibolites. Nevertheless, the new analyses help to confirm 



