123 



Two estimations in a Cooke apparatus, solution being complete 

 after two grindings, gave 1'21 per cent., which was taken as 

 correct. It will be seen from this that there is considerable 

 haematite in the norm which enters the modal ilmenite, the 

 composition of that mineral being according to the figures 

 derived from the calculation of the norm: Fe, O3, 62 per 

 cent. ; Fe O, 17 per cent. ; Ti O3, 19 per cent. ; Mn O, 2 per 

 cent. ; Ni, Co O, 1 per cent. — a composition not unusual for 

 this mineral, except in the presence of Ni, Co O. These, how- 

 ever, may be present modally in the pyroxenes. 



Again, the analysis confirms the determination of the 

 pyroxene as a diopside very poor in ferrous iron. The plagio- 

 clase of the norm is more acid than that of the mode, which 

 is very suggestive of the presence of considerable soda in the 

 potash felspars. It is obvious also that the formation of epi- 

 dote would render the modal plagioclase more acid, as it in- 

 volves the subtraction from the felspar of some of the anor- 

 thite molecules. The little normative quartz and hypersthene 

 has not been noticed modally. With these minor exceptions 

 the rock may be said to possess a very normative mode. The 

 classification shows the close affinity between this rock and 

 the tonalites. 



An interesting type of rock (slide 542), an alteration pro- 

 duct of the intrusive mass, was obtained from a road-metal 

 heap just outside Inglew^ood (see plate iii., fig. 4). It is to 

 be regretted that this was not obtained in situ, but it is pro- 

 bable it came from one of the quarries that lie about a mile 

 south or south-east of the Inglewood Hotel. What adds an 

 especial interest to this rock is that it is clearly identical with 

 the scapolite-amphibolite described by Dr. Woolnough from 

 Blakiston.(i'^) I have examined sections of his rock and he 

 of mine, and the similarity is very striking. The occurrence 

 of very pale-green actinolite and of scapolite in poikiloblastic 

 areas is common to both, so that I quote here Dr. Woolnough's 

 description of the Blakiston rock as applied with modifica- 

 tions to the Inglewood specimen : — "The rock consists essen- 

 tially of actinolite and scapolite. The structure answers 

 admirably to the description of poikiloblastic structure given 

 by Grubenmann. Actinolite. is the most abundant constitu- 

 ent. At first sight it appears to be irregularly scattered about 

 in stumpy rods, here and there aggregated into masses and 

 irregularly bounded poikiloblastic areas. The masses are, 

 however, crystal grains, and the surrounding rods are in 

 optical continuity with them. The optical orientations of 

 adjacent areas are quite independent, and in no way influ- 



(17) Trans. Roy. Sec, S.A., 1908, p. 136. 



