610 MR. A. K. COOMABA-SWAMI ON [Aug. 1 900, 



forms in quartz-veins. It is curious that the flakes and scales of 

 graphite often show on their surface a system of lines, perhaps 

 representing cleavage-cracks, which intersect at angles approxi- 

 mating to 60 c , 90°, and 120 . 1 



The graphite-veins contain numerous inclusions. Dr. Diersche 

 mentions quartz, iron-ore, orthoclase, hornblende, mica, apatite, 

 calcite, and especially rock-fragments, as occurring included in the 

 graphite of Ragedara, where the matrix consists of normal and 

 pyroxene-granulites. The rock-fragments included specimens of 

 these rocks, also a granite and a quartz-felspar-garnet-rock with 

 muscovite, and very large zircons and apatites. None of these rocks 

 seems very far removed from possible varieties of the matrix. 

 Hence we may hope to gather some evidence concerning the origin 

 of graphite as a vein-stone from the relations existing between the 

 graphite-veins, the contiguous matrix, and the included fragments. 



Two specimens from Ragedara show these relations well. The 

 first, a greenish pyroxene-granulite, is surrounded on three sides 

 by a graphite-vein varying in thickness from 2 to 20 mm. The 

 stalky graphite is arranged compactly, perpendicular to the surface 

 of the rock. A thin section has been made, including about | inch 

 of graphite and rather more than | inch of the rock. Held up to 

 the light, it shows a sharp division between the opaque graphite and 

 the semitransparent rock. Under the microscope, it appears that 

 graphite is absent from the greater part of the rock, but that as 

 one approaches the junction between rock and vein, the former 

 becomes thickly speckled with dusky graphite, and plates and scales 

 of graphite appear inclined at various angles. The rock is perhaps 

 rather less well preserved in this narrow zone next the vein itself, 

 suggesting infiltration. 



In another specimen from the same locality the relations between 

 rock and graphite-vein are clearly seen on a larger scale (fig. 4, 

 p. Gil). The photograph represents a smooth surface taken by 

 reflected light, so that the graphite appears white, the rock 

 mottled grey. The vein is of flaky graphite, the veins being as usual 

 perpendicular to the rock-surface : about | inch of graphite and 

 2| inches of rock are seen. For about j inch from the vein the rock 

 is impregnated with scales and flakes of graphite, some of the flakes 

 occupying tiny cracks in the rock. This graphite-bearing zone 

 looks rather less well preserved than the rest of the rock, which is 

 compact and hard and contains no graphite. 



Some specimens from Nilhene graphite-mine are slightly 

 different. Here the rock on or in which the graphite is found is 

 probably a vein-product (see p. 605). From two specimens (one of 

 which has an external graphite -vein of the usual t3 7 pe, the other 

 having two or three. veins running through it) thin slices have been 

 prepared. The rock-portion of the first specimen consists of quartz, 

 calcite, augite, scapolite, and sphene. There is a sharp junction 

 between it and the graphite, none of the latter being present in the 



1 Diersche [30] pi. vii, fig. 5 & p. 277 ; Rauff [25]. 



