1-2 HOLLAND: CHARNOCKITE SERIES. 



exposures of the charnockite series at St. Thomas' Mount and the 

 adjoining hills of Pallavaram may be con- 



Charnockite and Norite. , 



veniently placed first in the list of occurrences 

 of this series in South India. It is from this locality that large 

 quantities of the rocks have been quarried for structural and orna- 

 mental use in Madras, and it is from the neighbourhood of St. 

 Thomas' Mount that the rock of Job Charnock's tombstone was 

 obtained (vide supra, p. 134). 



The low hill on the west side of St. Thomas' Mount is composed 

 of a mass of charnockite in the centre, with masses of augite-norite 

 on the north-east and south-west sides. The central mass has been 

 selected as the type mass of charnockite (No. 9*658), whilst the sides 

 may be regarded as type examples of augite-norite (No. 9*657 on the 

 south-west side, and No. Q'66o on the north - 



Charnockite-pegmatite. , , , 



east). Both rocks are penetrated by veins 

 (contemporaneous veins) of a rock composed mainly of blue quartz 

 and microperthitic microcline which on account of its coarse grain 

 may be called charnockite-pegmatite (No. 9*659). 



The main mass of St. Thomas' Mount itself is augite-norite 

 which, however, is so cut through by acid veins, that in places the 

 rock becomes an irregular mixture of charnockite and norite such 

 as characterises the varieties described as " intermediate." 1 



St. Thomas' Mount, or " The Mount " as it is often called in 

 Madras, is only eight miles south of the city, on the South Indian 

 Railway ; so the locality is easily visited during the time that most 

 of the steamers are delayed in the harbour. The type-exposures are 

 thus easily examined by visitors who may not be able to make a 

 tour through the Presidency. The hill rises to about 250 feet above 

 the sea-level and is crowned by a curious old church built by the 

 Portuguese in 1547. 



The railway station of Pallavaram, 3 miles further south on 



the South Indian Railway, is situated between 



Garnetiferousleptynite. ^ q^^ vi , ]age (Isa .p a H avaram) and a 



* The common occurrence of what Lossen called Primaririimer in this series is 

 rfcfeired to in another section of this paper (p. 218). 



( 54 ) 



