cc Journal of the Asiatic Society of Bengal. [X.S., XIII, 



amounts of calcite, pyroxene (diopside), quartz, orthoclase and microcline 

 with a little plagioclase, biotite and sphene. Occasionally there is a little 

 graphite and pyrite, scapolite, wollastonite, zoisite and minute pale 

 garnet grains (grossularite), with large developments of idocrase (vesu- 

 vianite), at one or two places. 



These rocks occupy a considerable area in the northern part of Idar , 

 and though they may merge into another division of the Aravallis, the 



S 6 , f St0neS (which I must not sfc °P now to describe) in one 

 direction and into a non-calcareous biotite gneiss in the other, they dis- 



£mestones ,8 et S c & " y e ° f a P assa g e infco unmetamorphosed ordinary 



varJt il^r 11 y .° Ur a ! tontio "' however, particularly to two interesting 

 of dinSdi 1 calc ; gn .! ,8S aS , th T developed, one consisting very largely^ 

 and Z "Itt W ° lla f ston,te and s P hen o and with no free quartz of calcite, 

 ereat rnatL 7 e -J a PP eann S c i° se U P against the Idar granite in which 

 turToh Tot Zf T 5e A roC , k r haVe been developed as a close contact- 

 series o *A™*tf y , And J W ° Uld fUFfcher remark ^^t in another 

 Sets outer™ L T * fy* «?** J* miIf " awav from the nearest calc- 

 altered T»tT' and eon f st, og of a thick series of generallv but slightly 

 wSe selim ' tfr S n Ca ! Careous ' siliceo "s rocks and simple limestones, 

 abtTotrtTlnthL gm : n T y ° pni0n is beyond doubt, I have been 

 a^ Vxa Him t P ?' ty ° f ^f M intrusion of the Idar granite, 

 pvroine rdZ H^ rft m6n \^ minerals ft « Just referred to, the 

 greater LrtTfi i ° wollastonite and sphene making up^ the 

 Prims aEouncL \ Zt "i ^ nely « ranuli tic condition and with large 

 Features of SSSoSK of . ,doCT *»- There are many other less salient 

 the cXgneiss in an ^nnt d ^ edlraen tary series that further link it up with 



facts at g pub,ished ne IS/^ that l mi « ht adduce > *>"*> «*»tu the full 

 stron- J<mrnentl\^Lt fu^l perhaps be accepted as being a very 



roetZo^ztzz^:rt h :p of the ° rigin ° f the ca,c - gneiss by 



stratified with each XrinT^ Calcareous sediments which (all inter- 

 such as are used for ^r-H^ endless /t petltion > comprise dark slates, grits, 

 As regards thf oS ■ ^ ^^ and ord ' na ry soft limestones. 



fact that, though thevwlK '' '* ls nece ssary to emphasise the 



India, and thong the? stU] ?J™ * ^^ pU7zle for a lon * time in 

 concerning the serial and narS l T Y attr active problems to work out 



the general tendenov TtCll £ oZ* 1 "?™^ °[ the ^^ mineralS ' 

 rocks as having oriffinaV^T ? workers on them is to regard these 



hybridi™, from. a r, s g ed n ime e nt a b r y y % TT^ ^^ ^ "* 

 ticular, supposed DnpumarMi./ i raust P ass over here the P ar " 



veins, as aLuniing for hJ Lb^TV' the ^ eCted granite apHte 

 rocks in order briefly to refer tnnnI.- tUPes ° f these veT y interesting 

 in reference to the great ovtriS r aspect of the Idar Archaeans 



However m^^e^^^T 8 ? th ° Delhi ^^Ate. 

 Dharwar quartzites, H would be a W the sedi ™ntary origin of the 

 mous thicknesses and extension V? u T" who wo " ld declare the enor- 

 bedded and sometime eveTrinn. ^ fre ^ently well-bedded, current 

 Rajputana and many other ^„ P P ru" marked c l ua rtzites (Imown all through 

 Quartzite) to be anything ^w ♦K° Unng dist "'cts and states as the Delhi 

 fact that it has generally become o & d *i ? dim entary rock-in spite of the 



And yet these rocks IT Com P let ely recrystallised. 

 State by perfectly continuonLvr° Ped in Idar and as traced into that 

 exhibit the most incongr °o u E^ F° T &n enorm ous area of country. 

 In their broad aspects tHat fit'? P3 to the und erlyin g Aravallis. 

 s.milar to the proved unconformif 3U ggest an unconformable overlie 



Alwar ; but, examined in detail y ? een ln raor e northern sections such as 

 tic synclinal trough arrangement ' S n0t found fc o hold, no characteris- 

 and ranges of these roclfa nn«L^ er ra anifesting itself, and the ridges 

 general direction of the ran^ I i lng P la g'oclinal strikes as regards the 



range, and outcrops up against the AraVallis at 



