Vol. 56.] CEYLON ROCKS AND GRAPHITE. 593 



characteristic greasy look. As a rule, foliation is not evident 

 macroscopically, but it may appear in the thin slices. The minerals 

 most frequently present include pyroxene (augite or hypersthene, 

 or both), felspar (plagioclase, usually labradorite ; more rarely 

 orthoclase-microperthite), garnet, quartz, amphibole, magnetite* 

 biotite, apatite, and zircon. Of these the pyroxene and felspar alone 

 are essential constituents ; in the absence of quartz and garnet the 

 rocks approach gabbro, while varieties consisting chiefly of pyroxene 

 and garnet are near to eclogite. The structure is often granulitic, 

 the minerals being much interlocked, and the quartz-grains elon- 

 gated as in the normal granulites ; or it may be merely granular. 

 Centric structures taking the form of pyroxene-felspar-intergrowths 

 surrounding garnets are very characteristic of some varieties. In 

 the Eagedara granulite the felspar is orthoclase-microperthite, 

 and the garnets are intimately associated with brown mica. The 

 centric structures appear to have arisen in connexion with the 

 corrosion of the garnets. 



Among the specimens collected three types are recognizable : — ■ 



(i) Plagioclase-bearing pyroxene-granulite with centric structures ; 

 (ii) Orthoclase-bearing pyroxene-granulite with centric structures ; and 

 (iii) Granular pyroxene-granulites without centric structures. 



Type 1. NeweraEliy a. — A specimen collected on the path lead- 

 ing up Pidurutalagalla, about one-third way from the summit, has 

 proved interesting. The rock is dark green, and contains dark red 

 garnets. The minerals are hornblende, pyroxene (chiefly green 

 augite ; a little hypersthene), plagioclase (27° 27°, probably labra- 

 dorite), magnetite, apatite, and zircon. The garnets are not quite 

 evenly distributed. In parts free from garnet, hornblende is more 

 abundant than augite, and these two minerals, with plagioclase and 

 quartz, compose a granular rock. In the neighbourhood of the 

 garnets, augite is far more abundant than hornblende, and magnetite 

 becomes conspicuous. Some parts consist almost entirely of garnet 

 and augite, thus resembling eclogite. Throughout there is a limited 

 amount of a pleochroic (pink to sea-green) pyroxene, probably 

 hypersthene. Only when the garnets are in contact with plagioclase 

 rather than augite are the remarkable coronas seen. These 

 consist of radiating fingers of pyroxene (augite, hypersthene) pro- 

 ceeding from the garnets and standing out against a plagioclase- 

 background, the plagioclase showing between crossed nicols the 

 usual twin-lamellation, which is not interfered with by the fingers 

 of pyroxene. The larger magnetites of early consolidation are 

 curiously related to the garnets. They are quite irregular in shape, 

 and occupy bays and depressions in the garnets, but are separated 

 from them by straits of plagioclase constant in width. The 

 garnet appears to have been moulded on the magnetite, and sub- 

 sequently separated from it by a narrow strip of felspar. From 

 the almost ophitic way in which the plagioclase associated with the 

 coronas and straits occurs, it appears to have been the last mineral 

 to consolidate (PL XXXIII, figs. 3 & 4). 



Eagedara. — In one specimen from Eagedara somewhat similar 



