154 R. A. Farquharson — Petrology of N. Kalgoorlie, 



directions, and surrounded by almost isotropic green chlorite. 

 Crystals of carbonate are also visible, and there are occasional small 

 plates of quartz. Brown-yellow rutile is rather common in grains 

 and prisms. 



12315 (shaft about 80 ft. S.E. of S. corner of G.M.L. 4161 E.) 

 is a reddish rock with small plates of quartz, areas of greenish 

 chlorite, many small brilliantly polarizing flakes that have been 

 referred to talc, and numerous brown-red dusty aggregates and 

 crystals. As the latter show in places distinct rhombic forms, they 

 are, in all probability, forms of ferriferous carbonate that have been 

 oxidized. Veinlets of quartz penetrate the rock. 



12366 (dump 1 1 ch. N.N.W. of N. corner G.M.L. 4337 E.) is 

 a soft greyish-green rock with a reddish tinge. There are again 

 ferrifei'ous carbonate crjstaLs, and remains of small twinned, 

 columnar, or lath-shaped crystals of felspar. The rock is of doubtful 

 origin. It may be either a chloritized or somewhat carbonated form 

 of the keratophyre, or it may be of amphibolite origin. 



11083, " Tabby Cat" ((iibson), is a talc-chlorite rock with crystals 

 of a carbonate. There are pleochroic halos round brown and black 

 crystals of ilmenite in chlorite. 



D. EocKS OF Doubtful Origin. 



1. The FucTisite Hocks. 



These specimens are more or less identical in appearance with 

 those already described by the writer from other localities,' with the 

 exception of 12317, which is a pale-green quartz rock with green 

 micaceous scales in strings on the surface ; they are all heavily 

 carbonated, partly siliceous, with white quartz, and to a greater 

 or less extent pyritic. The fuchsite' occurs in films and scaly 

 aggregates all over the rocks. Most noteworthy, however, as tending 

 to throw some light on the mode of origin of the rocks, is the 

 occurrence in 10439 of a development of tourmaline needles, associated 

 with a fresh felspar and large idiomorpliic crystals of a carbonate. 

 The nature of the felspar has not been definitely established, but from 

 measurements already made it appears to be albite. The significance 

 of the occurrence of tourmaline has already been pointed out. The 

 origin of the chromium oxide that has given rise to the fuchsite is 

 still, however, to be accounted for. Attempts have already been 

 made to explain its origin in definite terms, but one great difficulty 

 has been that for various reasons no field evidence of its occurrence 

 of any service can be obtained. The same difficulty has been met 

 ■with in the area under consideration. The specimens were obtained 

 from dumps of shafts to which access is no longer possible. The 

 chromium must, however, be regarded either as original in the rock 

 or as introduced by circulating lateral or ascending solutions to which 

 the carbonates, the silica, and indirectly the tourmaline are due. 



^ Bulletin No. 43, G.S.W.A. : Observations on some Bocks from Ingliston, 

 Extended Mine, Meekatharra. Also Bull. No. 47, G.S.W.A., Petrological 

 Notes, p. 92. 



