1336.] 



Neelgherries and Koondahs. 



257 



appearance so common in the granitic hills in other parts of India. 

 The granite occasionally is of a dull, yellowish brown colour, owing to 

 the felspar, which assumes that tint, resembling in Unit state the feui lie 

 morte of the French. Doctor Hardy has remarked the same change 

 of colour in the granite of Mewar. 



The other species of granite, found always associated with the former, 

 is the pegmatite (No. 33), a rock composed of only two minerals, fel- 

 spar and quartz. The places where I have found this rock in situ are 

 marked in the map: it is a variety of the graphic granite; in aspect 

 very different from the same rock found in other parts of Southern 

 India, in which the quartz is regularly crystallized, and the felspar in 

 long slender crystals, of a pale flesh colour. 



In the variety of this rock on the Neelgherries, the felspar is milk- 

 white, lamellar; but not in regular prismatic crystals: the quartz is 

 occasionally of a smoky colour or bluish ; and in angular pieces, this 

 colour is sometimes so deep as to appear nearly black. In some of the 

 masses are occasionally seen a few garnets, or a little hornblende; but, 

 in general, the rock is exclusively composed of the two minerals, fel* 

 spar and quartz*. 



Of this rock some erratic blocks are seen in the valleys, at the foot 

 of those hills, the summits of which contain it in situ : this is the case 

 in the Kaitee valley, whither many of these boulders have been probably 

 hurled down either from the summit of Doodabetta, or f»om the Kaitee 

 peak, where pegmatite is found. 



It is undoubtedly from the decomposition of these masses, that the 

 porcelain earth, described in the beginning of this Memoir, arises. 

 By comparing specimens of the two, their identity is established. 



The sienitic granite varies in the proportion of its component 

 minerals, and therefore in appearance ; sometimes approaching diabase 

 (primitive greenstone), and at others, granite (No, 331). It almost 

 always contains garnets as one of the minerals composing it ; and 

 when this mineral is abundant in the rock, the quartz diminishes in 

 proportion. In the Doodabetta group, I have remarked, in some 

 places, the garnets, instead of being either amorphous, or in angular 

 crystallized pieces, assume the granular form, resembling colophonite ; 

 in which case, the rock containing it assumes a stratified appearance 

 (No. 34), and at others being lamellar, and of the dodecahedral species ; 

 in this cas' j , it resembles cinnamon-stone, or essonite. 



The hills, confining the valley of Kaitee, being formed of rocks con- 

 taining curious and rare varieties of minerals, possess, to the eye of the 



* This species of granite seems to be very common in many parts of India.— Dr. 

 Hardy appears to describe it in many localities, in his sketch of the Geology of Central 

 India. Many of the Vo -ks jutting up in the plain between Palaveram and Madias, such 

 as that near the Race Course, are all pegmatite* 



