614 ME. A. X. COOMAKA-SWAMY ON [Aug. I90O, 



Pyroxene-granulites are widespread and characteristic ; 

 their mineral composition is rather various. Certain structures in 

 connexion with garnets are very characteristic of some types ; 

 they appear to result from the corrosion of the garnets by the 

 magma. Normal granulites are also abundant; they are 

 typically white or grey, and contain currant-red garnets. The granu- 

 litic structure and much elongated quartz-grains are characteristic. 

 Microcline-gneiss, sometimes with hornblende, occurs in steep 

 dome-like hills, originating the term domoid gneiss employed 

 by Prof. Walther. Anorthosite-gneiss, gneissic granite, 

 and pegmatite are also found, the latter occurring in veins, but 

 very rarely. Other rocks include dark diorites and hornblende- 

 gabbro. A quartz-norite containing large individuals of 

 hypersthene occurs near Kurunegala. The white crystalline 

 limestones often contain pale mica and blue apatite; in some, 

 colourless pyroxene is very abundant. 



Banded scapolite and wollastonite-bearing rocks are 

 found at Galle. Certain rocks similar to these, but apparently 

 vein-products, are also described ; these contain in some cases quartz 

 and calcite micrographically intergrown. 



Graphite occurs chiefly in branching-veins in igneous rocks, 

 which at llagedara are granulites and pyroxene-granulites. The 

 relations to the matrix are described, and are held to favour the idea 

 of the deposition of the mineral as a sublimation-product (Walther), 

 or from the decomposition of liquid hydrocarbons (Diersche). 

 Chemical analyses of several minerals, including manganheden- 

 bergite, are given. 



EXPLANATION OF PLATE XXXIII. 



[Photographs taken by ordinary light, except fig. 1.] 



Fig. 1. Quar tz- calcite - micropegmatite from Nilhene graphite- 

 mine. x33. Taken between crossed nicols. (See pp. 6U5, 606.) 



2. Pyroxene-gran u lite from Ragedara. X 15. 



This shows garnet, corroded and surrounded by orthoclase-micro- 

 perthite, and intimately associated with brown mica. (See p. 594 & 

 text-fig. 1.) 



3. Pyroxene-granulite from Pidurutalagalla (Newera Eliya). 



X 15. 



This shows garnets with fringes of pyroxene-plagioclase intergrowth 

 (as in fig. 4) on one side; the garnets on their other side are in 

 contact with the augite. A second generation of iron-ore is associated 

 with the pyroxene-fingers. (See pp. 593, 606.) 



4. Pyroxene-granulite from Pid uru talagalla (Newera Eliya). 



X 15. 



The black portions are magnetite ; they are separated by narrow 

 strips of plagioclase from the garnet which has fringes of pyroxene- 

 fingers projecting into the plagioclase ; in the upper middle part of 

 the figure a whorl of radiating pyroxene-fingers has for its centre a 

 very small (residual) fragment of garnet. The remaining portions 

 are chiefly pyroxene (augite). (See pp. 593, 6C6.) 



5. Orthoclase-microperthite from K a 1 a w e w a. X 24. 



The right-hand crystal shows the cleavage parallel to OP in both 

 felspars. (See pp. 597, 608.) 



6. Hornblende - gabbro from the Battenberg Battery, 



Colombo. X 13. (Seep. 598.) 



