Vol. 56.] CEYLON KOCK3 AND GRAPHITE. 605 



Nilhene graphite-mine. — Specimens from this locality are 

 very similar in petrological characters to those described from Galle. 

 They differ chiefly from the Galle rocks in being associated with 

 vein -graphite ; in the presence of a micrographic intergrowth of 

 quartz and calcite in some cases ; and in the greater abundance of 

 calcite. 



A specimen associated with a vein of graphite (see p. 610) may 

 be described in detail. The minerals are quartz, calcite, augite, 

 scapolite, and sphene. The augite is of the usual pale green, with 

 extinction-angles ranging up to 44° : the smaller individuals join in 

 a pegmatitic structure with the quartz and calcite ; but with larger 

 grains this is only true of their border. The intergrowth of quartz 

 and calcite is such, that in a small area the quartz and calcite 

 severally extinguish uniformly (PI. XXXIII, fig-. 1). In other parts 

 of the slide there is merely a quartz -calcite mosaic. The scapolite 

 is recognized by its rectangular cleavage and negative uniaxial 

 interference-figure, etc. 



In other specimens the mineral associations are : — 



(1) Quartz, calcite, and graphite (scattered) ; 



(2) Augite, scapolite, orthoclase, wollastonite, graphite, sphene, iron-ore, and 



calcite ; 



(3) Orthoclase, augite, sphene, magnetite, graphite, calcite, quartz : the quartz 



and calcite forming a mosaic in small patches, probably replacing 

 wollastonite ; 



(4) Orthoclase and scapolite ; 



(5) Quartz, orthoclase, and graphite. 



In many of these cases a small quantity of an undetermined 

 mineral is present. It occurs in sheaf-like aggregates or in radi- 

 ating flakes, in connexion with the nests of stringy and dusty 

 graphite. Cleavage parallel to the length of the flakes is well- 

 marked, less commou is one perpendicular thereto. Extinction is 

 parallel to the principal cleavage. The mineral is colourless, and 

 has a low refractive index, bright interference-colours, and strong 

 double refraction. It does not appear to be muscovite. 



These rocks, some of which, as I said, are associated with vein- 

 graphite, are very probably themselves rather of the nature of 

 vein-products (see p. 610). 



Ambakotte (near Kandy). — At the Gangapitiya moonstone- 

 pits occur, besides the normal granulite, some curious banded or 

 nodular rocks. Some specimens show straight, or more or less 

 concentric, zones of grey, dark green, and white rock. The grey 

 inner part seems to consist almost entirely of grey granular augite, 

 rarely showing cleavage. The succeeding green band (reaching 

 about \ inch in width) contains augite, plagioclase, spinel, and an 

 abundant pleochroic undetermined mineral, the two last-mentioned 

 giving the green colour. The undetermined mineral is pale greenish- 

 blue by transmitted ordinary light, and is strongly pleochroic 

 from pale green to sky-blue : multiple twinning is conspicuous ;. 

 the appearances suggest a ferromagnesian mineral. The spinel 

 is granular, pale green, and has a very rough surface. Dusky 



Q. J. G. S. No. 223. 2 s 



