20 MIDDLKMISS : Til E G E( >\A H i S UK IDAIl STATI.. 



is furnished by the southern end of the hill where the position is as 

 follows (in the section below text fig. 2). The evidence is sufficiently 



S.W. 



Fte. 2. 



Idctr 

 Granite 



N.E 



conclusive for the age of the calc-schist and also probably for its 



interbanded aplite veins being distinctly older than that of the 

 Idar granite. 



The second feature characterising the junction section is the 



production in the calc-gneiss of rich and thick 



Idocrase rock ; , . , . . 



hands ot idocrase (vesuvianite) rock. Idocrase 



is a common mineral developed in limestones by contact meta- 

 morphism of this kind, but the record of this mineral in India is a 

 very insignificant one. Beyond being simply mentioned in lists 

 of minerals from the Nilgiris (see H. Congreve, Madras J own. 

 Lit. and Science, Vol. XXI 1. p. 248) and also from Manbhum 

 {Mem., Geol. Surv. India, Vol. XVI II. p. 103) the only place 

 whence specimens are represented in the Survey -Museum is 

 Tonk State, where from a quarry at Her a specimen of " egeran " 

 was obtained (see Mallet, Man. (leal. India, Mineralogy, p. 93) 

 its registered number being IT. 779. Mr. Vredenburg, in his 

 determination of specimens collected by Prof. Page (see ante p. 2), 

 doubtfully recognised the mineral microscopical I v in the Jdar 

 granite, a statement which so far I have been unable to verify. 

 From the fact that I have now found it so abundantly as a contact 

 phenomenon in the zone of calc-gneiss bordering the Tdar granite, 

 it is quite likely that Mr. Vredenburg's determination is correct 

 In the present instance the calc-gneiss (. 5 2 ./ 5 , 121o2) contains, 

 in addition to idocrase, all the ordinary minerals that compose 



