52 fcilDDLEMtSS: THE GEOLOGY OF IDAR STATE. 



Where the darker bands become coarser in grain and the blades 

 of amphibole more pronounced, the latter 

 'Feather' Ampin- still have the ' filigree ' appearance so well 

 bohLo " marked that their resemblance to the variety 



named 'feather amphibolite ' by Adams and Barlow (/or. Git. p. 

 158 and plates XXXVII and XXXY111) is very striking indeed, 

 except that I have not seen in my area any specimens so coarsely 

 crystalline as those of the Ilaliburton and Bancroft area. In 

 nearly all other respects, the identity in the habit of the amphibole 

 and its associations with the ground-mass, and finally the closely 

 set, banded arrangement of the amphibolite with the crystalline 

 limestone, is almost an exact counterpart of those described and 

 figured by Adams and Barlow. The only principal mineral not 

 found by me in these rocks, and recorded by the authors above, 

 is pyroxene. 



Chiefly owing to this absence, and to the suddenness of the 

 change to the calc-gneiss with abundant diopside, has it been im- 

 possible to link the one rock (amphibolite) with the calo-gneiss. 

 It is possible, of course, that the junction may not be a natural, 

 but a faulted, one ; in which case any transition layers might have 

 disappeared in the break. 



The rocks as exposed in the more continuous little ridges a 

 short distance across the Sabarmati river in Danta State were 

 only glanced at hurriedly by me. So far as they were seen, they 

 suggested dark grey marbles weathering a yellowish-grey colour, 

 with a little phyllite containing small garnet grains. 



In the bed of the Sabarmati river one solitary band of fine- 

 grained biotite-granite, six feet in width, No. 5 *ft (12339), was 

 observed as the sole intrusive rock in the area. It cuts discordantly 

 across the edges of the amphibole limestone, but was more of the 

 nature of a fine-grained variety of the Idar granite than of the 

 aplites so characteristic of the calc-gneiss. 



In the area covered by this description (partly perhaps owing 

 . to the limited exploration which I was able 



I ncertain origin of x 1 i r ,„„+^,> 



the Amphibolite Lime- to effect owing to the season, lack ol water 

 Btones. am | thei reasons) T was unable to come to 



any conclusions, from the local evidence, as to the origin of these 

 rocks, especially with reference to the question whether hl-par-W 

 intrusion, or metamorphism of impure calcareous sediment, was the 

 method of their inception. Their similarity to the series described 



