602 



MR. A. K; COOMARA-SWAMY ON 



(12) Pegmatite. 



[Aug. 1900, 



Veins of coarse pegmatite traversing other rooks seem rare in 

 Ceylon. They were only seen in a quarry by the roadside between 

 Wattegama and Pamvile. 



Much of the rock exposed at Ambalangoda is pegmatitic in the 

 true sense. Thus, in some cases, fairly large idiomorphic individuals 

 of hornblende and orthoclase are embedded in a quartzose matrix. 

 It appears that graphic granite is brought from Ambalangoda, bat 

 I did not find this rock, although traces of graphic structure are 

 abundant. 



Fig. 2. — Section near the flagstaff, Oalle Fort, showing mineral- 

 handing in the sea-polite- and ivollastonite-bearing rocks. 





[Below the letter A in the figure a 2-foot rule is seen.] 



(13) Rocks of Unusual Composition. 



Galle. — The rocks now to be described from Galle are peculiar 

 in their petrological characters and mineral composition. They are 

 specially marked by the presence of scapolite, wollastonite, and a 

 green monoclinic pyroxene (spoken of as green augite, but probably 

 in each case having a composition near that of manganhedenbergite 

 — see analysis, p. 604). The conspicuous mineral -banding and the 

 tendency in the wollastonite to mould itself on the other minerals 

 are noteworthy. The peculiar conditions giving rise to rocks of 



