406 Arthur Holmes — The Granophyres of Carrock Fell. 



The following analysis of the Brandy Gill granophyre was made by 

 Dr. H. P. Harwood :— 



Percentages. 



SiOa 



A1 2 3 



Fe 2 3 



FeO 



MgO 



CaO 



Na 2 



K a O 



H 2 + 



H 2 0- 



C0 2 



TiOs 



P 2 5 



MnO 



S . 



BaO 



Zr0 2 



100-40 

 Less for S. 0-03 



Molecular 

 Proportions. 

 1-3353 

 •1047 

 •0004 

 •0068 

 •0157 

 •0180 

 •0555 

 •0151 

 •0444 



•0273 

 •0011 



•0007 

 •0028 



•0002 



Mineral Composition. 



Total 



100-37 



Quartz . 

 Albite . . 

 Muscovite . 

 Kaolin . . 



Hypersthene 



Magnetite . 

 Ilmenite . 

 Pyrite . . 



Zircon . 



Dolomite . 



Calcite . 



Water . 



Less O for S 

 Total 



53-57 



29-08 



12-12 



1-00 



1-23 



0-09 

 0-16 

 0-17 



0-04 



1-66 

 0-90 



0-40 



100-39 



The analysis is remarkable for the high percentage of silica that it 

 reveals. The highest percentage found in the estimations made for 

 Dr. Harker was 77 # 38, while in the specimen analysed by Mr. Barrow 

 the silica amounted to 71 '60 per cent. 1 The high alumina relative 

 to alkalies has been interpreted above. The abundance of soda 

 compared with potash justifies the name, albite-granophyre, applied 

 to the rock. 



AXBITE-QUAHTZ-POKPHYEY. 



The distinguishing features of this rock have already been stated 

 above. The specimens are from one of those portions of the 

 "granophyre" which "show little or no graphic structure at all, 

 the quartz and felspar forming an irregular mosaic. In this case the 

 quartz tends to occur partly in larger crystal-grains, and the rock 

 approximates to some quartz-porphyries ". To this description 2 there 

 is little to add. The felspar is again albite, and quartz, which is 

 very abundant, corrodes the felspar and is itself corroded by the 

 groundmass. Muscovite occurs in larger wisps than in the grano- 

 phyre, and also forms curious vermicular aggregates in the ground- 

 mass. As in the granophyre the rock contains narrow veins of 

 quartz, and smaller ones containing carbonate minerals. The 

 remaining minerals were determined by separation with Thoulet 

 solution, using much more material than was available of the 

 granophyre. The crop of heavy minerals proved to be identical with 

 that obtained from the latter, except that in the residue remaining 



1 A. Harker, loc. cit., pp. 129-30. 



2 Harker, loc. cit., p. 128. 



