IDAR GRANITE, GRANOPHYRR, ETC. 



121 



and there are the usual minor accessories of iron ores, apatite, 

 sphene, zircon, together with the rarer mineral topaz in one case. 

 Muscovite is absent as an original constituent. 



So far as it goes this is borne out by the single complete chemical 

 analysis that has so far been made. The 



Chemical composition. ... , 



analysis is of one of the hornblendic varieties, 

 which, on account of the amount of plagioclase relative to the potash 

 felspar present, seems to lie near to adamellite or monzonite. The 

 specimen is from Kawa on the western side of Idar State (lat. 23° 

 52', long. 72° 57'), and the analysis was made by Dr. Christie 

 in the Geological Survey laboratory. Although this variety is 

 fairly commonly distributed in the State it is not as prevalent 

 as the biotite variety : there can be no doubt that the standard 

 type as found round about Idar town would be on the whole richer 

 in potash than the sample chosen for analysis, which was taken 

 for other special reasons. 



Analysis of Idar granite. 



(Hornblende variety. ) 

 Kawa 



SiO, 

 A1,0, 



Fe 2 0, 



FeO 



M,(» 



CaO 



Na,0 



K..O 



H,0 (below 1 



II, n (above 1 



TiO, 



Zr0 2 



CO, 



P 2 5 



CI 



so, 



Cr 2 3 

 MnO 

 BaO 

 SrO 



us 



66*04 



14-77 

 IIS 

 4-41 

 0*98 

 2-95 

 2*66 

 5-25 

 •21 



•71 



■69 



03 



trace 

 trace 

 trace 



•11 

 •02 



trace 



Specific Gravity^ 2-72 



99-91 



