MI2M0IRS 



OF 



THE GEOLOGICAL SURVEY OF INDIA. 



The SlVAMALAI series of El/eolite-syenites and 

 Corundum-Syenites in the Coimbatore district, 

 Madras Presidency. By Thomas H. Holland, 

 A.R.C.S., F.G.S., Officiating Superintendent \ Geological 

 Survey of India. 



I.-INTRODUCTION. 



In his description of the corundum-bearing areas in the Salem 

 and Coimbatore districts, Mr. C. S. Middlemiss has described the 

 rock of Sivamalai as a pale-grey gneiss " composed almost wholly of 

 plagioclase felspar and microcline in a granular condition " with biotite 

 or hornblende, iron-oxide and zircon (?) as accessories. This rock is 

 said to be invaded by veins of a coarse, red granite, from which the 

 villagers have for many years extracted considerable quantities ol 

 corundum, especially from diggings made near the junction of the two 

 rocks. 1 



Whilst examining sections of these rocks the author de- 

 tected the presence of graphite in some, and claeolite in all the 



1 Rec. Gcol. Saw., fnd. t VoJ. XXIX (1896), p. 47. 



( 1 ; 



