PETROGRAPHICAL NOTES. 77 



products so fine-grained as to be difficult to identify. The felspar 

 is almost completely saussuritised ; leucoxene is largely developed. 

 Another secondary mineral here makes its appearance, which wiil 

 be found always present in the rocks about to be described : 

 this is epidote which, in the present instance, may be observed 

 forming large granular aggregates. The rock, however, shows none 

 of the deformation and crushing of minerals which is so often 

 observed in other parts of the Son region. At this western 

 extremity of their outcrop the Bijawars are probably less disturbed. 



Nearly all the above-mentioned specimens contain micrographic 

 intergrowths of quartz and felspar. 



The series which we have just considered is far too incomplete 

 to allow a detailed study of the manner in which the gradual 

 metamorphism of the different minerals is accomplished, but it may 

 serve to give some idea as to the original condition of the rocks 

 which we are about to review, and also to show that the lavas 

 occurring in these two separate areas of the Bijawars belong to the 

 same class of rock. 



All the rocks which I have collected are considerably altered : the 

 micropegmatite, if it ever existed, has entirely disappeared, Except 

 in two specimens, the alteration of augite to hornblende is com- 

 plete. The change of ilmenite into leucoxene has proceeded so far 

 that frequently nothing remains of the original mineral. In addition 

 to these chemical changes the rocks exhibit conditions of strain and 

 crushing of the minerals. Epidote and chlorite are universally 

 present in large quantity, the latter mineral giving the rocks their 

 characteristic colour. Calcite is often largely developed. 



All the specimens contain crystals of secondary pyrites which 

 are conspicuous in the hand-specimen, but generally break off during 

 the preparation of microscopic sections. 



Referring to the diagrammatic section above represented (Fig. 5), 

 „. . we may first review the rocks composing the 



Rocks at Girvvr. J . 



more southern of the two main outcrops (6 in 

 diagram); 



( 77 ) 



