I (SO HOLLAND: CHARNOCK1TE SERIES. 



Types rich in Garnet, 



In the immediate neighbourhood of Salem there are several 

 occurrences of the garnetiferous basic members of this series form- 

 ing small, bare, rocky hills with apparently a lenticular outline ; the 

 hill immediately W.-S.-W. of Salem and Nagaramalai near the Chalk 

 Hills to the north of the town are good examples — Nos. 9*683, 9*684) 

 11*895,11*903. These are presumably amongst the rocks referred 

 toby Lacroix l as members of his "pyroxenic and hornblendic 

 gneiss, (£)", and which, quoting Leschenault's labels, he says forms the 

 valley of Salem. It is a little difficult to say what is meant by the 

 valley of Salem ; but these rocks are certainly not the most abundant 

 in the neighbourhood of the town, although, on account of the 

 abrupt little hills they form, and on account of the conspicuous 

 garnets they contain, it is likely that they would figure largely in the 

 " bag " of an amateur collector. 2 This particular type very com- 

 monly occurs in such lenticular masses in the schists and old biotite- 

 gneisses of the plains in the immediate vicinity of large mountain 

 masses like the Nilgiris and the Shevaroys. Those referred to here, 

 for instance, as occurring in the vicinity of Salem entirely resemble 

 the little hillocks which fringe the foot of the Nilgiris in the Bhavani 

 valley. 



These rocks are generally but not always coarser in grain than 

 the average basic varieties of the series. Sometimes they are very 

 hornblendic and at other times are comparatively free of hornblende. 

 In general the optical characters of this mineral and its fellow ferro- 

 magnesian silicates are in agreement with the data already recorded 

 for the other members of the series described above. 



One interesting peculiarity is the frequent correspondence in 

 the intensity of colour shown by the hyper- 

 sthenes and the garnets. Without turning the 



1 Rec. Geol. Surv. Ind., Vol. XXIV, p. 175. 



2 Leschenault de la Tour's only published reference to the exposures of these rocks south- 

 west of Salem is as follows: — " Une montagne dans le sud-ouest (of Salem,) est presque 

 enticement form£e de roches oii l'amphibole domine, et sur la surface desquelles des grenats 

 grossiers et opaques sont disposes par plaques." {Mem. du Mus. d'hist. nat., Vol. VI 

 (i8iO),p.343). 



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