108 R. A. Farquharson — Petrology of N. Kcdgoorlie, 



It is held from facts that can be established in this and adjoining 

 areas, with regard both to tbe lodes and the country rocks, that the 

 changes taking place progressively towards the most complex portions 

 of the field can be gradually traced, and identification made on 

 reliable evidence that may not be forthcoming in the latter. It may, 

 of course, happen that there are several points even at the beginning 

 that have to be left undecided, and we sliall see that this is certainly 

 the case in the North End, but it is hoped that the investigation of 

 the succeeding portion of the field will clear up the difficulties and 

 obscurities surrounding these. 



Though the writer was enabled to spend a few days going over 

 the ground, the field work has been entirely done by Mr. Feldtmann, 

 and the specimens representative of the area were largely collected by 

 the same officer, but the collection has been supplemented by the 

 specimens already in the Survey Museum which have been taken 

 from time to time by other offl.cers of the department past and 

 present, viz. Messrs. Beecher, Campbell, Gibson, and the Govern- 

 ment Geologist Mr. A. Gibb Maitland. 



2. Peeyious Liteeatuee. 



Practically nothing has been written so far on the North End. 

 Gibson ^ makes mention of it in places, but only in the most general 

 way. Larcombe- dismisses it with a reference to a plan and section.^ 

 He does not mention the appearance of any porphyrite (kerato- 

 phyre), though he notes that amphibolites occur at the North End. 



3. Classification of the Rocks. 



Altogether about sixty specimens have been sliced and examined.* 

 In the main, as regards colour, the rocks fall into two broad 

 groups : {a) those of a yellowish or brownish tint, and {h) those of 

 a greenish tint, which varies from greyish to deep green. The 

 former are, as a rule, hard, but the latter* are all in the soft, some- 

 what clayey rocks with a more or less pronounced soapy feel. Much 

 difficulty has been encountered in the study of the specimens. With 

 very few exceptions — some of the porphyrites and a few doleritic or 

 gabbroid rocks — the whole collection consists of specimens that have 

 been intensely altered, in some cases so altered that no trace whatever 

 of original structures now remain. In most cases only diligent search, 

 with high-power lenses, has enabled such clues as remains of felspars 

 and pseudomorphs and felspars and ferro-magnesians to be detected, 



1 Geol. Soc. W. Australia, Bulletin 42. 



" Loc. eit. 



•' Plate V, Geological plan and section of the Tea Gardens. 



^ Of those of this number that were obtained by previous collectors, two, 

 viz. Nos. 2918 and 11096, find no counterparts among Mr. Feldtmann's 

 collection. No. 2198 was obtained from the extreme north-west of the area 

 under consideration, and from a dump so weathered as to yield no specimens 

 of any service. The locality from which 11096 was brought has been noted 

 in such vague terms as to render it impossible now to trace the specimen in 

 the field. 



5 With the exception of Nos. 12322 and 12324. 



