, 7 HOLLAND: SIVAMALAI SERIES. 



specimens taken from the Sivamalai mass, and subsequent examina- 

 tion of the area, in company with Mr. Middlemiss, resulted in the 

 discovery of coarse-grained (l contemporaneous " veins in which the 

 crystals of elaeolite sometimes measured five inches across. At the 

 same time it was discovered that the elaeolite-syenite is accompanied 

 by masses of augite-syenite— a feature characteristic of its typical 

 occurrences in other parts of the world. The present occurrence of 

 this interesting rock is remarkable for the constant presence in it of 

 graphite and calcite, both of which are regarded as primary constitu- 

 ents, and for the association with it of corundiferous albite-orthoclase 

 rock. 



Notwithstanding the foliation of these rocks and at first sight 

 their resemblance and apparent conformity to the general crystalline 

 schists of the area in which they occur, the structures they present, 

 their chemical composition, petrological characters and associations 

 are in agreement with the peculiar features usually presented by the 

 family of elaeolite-syenites, and with these rocks, consequently, the 

 elaeolite-bearing members of this area are grouped. 



The so-called coarse red granite is very poor in ferromagnesian 

 minerals, practically devoid of quartz, and is essentially a felspar- 

 rock in which corundum sometimes occurs in quantity. 



The geological bearing of this paper is in consistent extension of 

 the principles defined in a previous memoir, 1 where reasons are given 

 for separating the charnockite series from the other crystalline schists, 

 and raising the family to the dignity of a petrographical province. In 

 the present instance we are dealing with a complex composed of 

 rocks varying considerably in composition, but nevertheless believed 

 to be genetically related to one another, and, in fact, to form a 

 definite petrographical province, igneous in origin and geologically 

 very ancient, possibly Archaean in age. 



1 Mtm, GeoU Surv., lnd. % Vol. XXVIII, p. 1x9. 



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