596 MK. A. X. COOMARA-SWAMY ON D^Ug. 1900, 



(2) Normal Granulites. 



These and allied rocks are abundant in Ceylon. They are 

 typically white or grey, and contain currant-red garnets; the 

 texture is compact or saccharoidal, and traces of graphic structure 

 are often recognizable. The quartz-grains do not contain lines of 

 fluid-cavities, and the rocks seem igneous rather than meta- 

 morphic. The minerals include quartz (elongated grains), felspar 

 (orthoclase- and microcline - microperthite and plagioclase), and 

 garnet, with often also biotite, magnetite, ilmenite, apatite, and 

 zircon. The microscopic structure is very granulitic : the minerals 

 being much and confusedly interlocked, and the quartz-grains con- 

 siderably elongated. 



Kandy. — A characteristic white saccharoidal granulite with red 

 garnets occurs in the quarry between the lake and the reservoir. 

 It is largely used for road-metal. 



liocks collected at the far end of the reservoir contain conspicuous 

 large garnets, sometimes in a white quartzose matrix, in other 

 cases forming with biotite a biotite-schist. In the paler specimens 

 the minerals are quartz, garnet, and plagioclase ; the last-named 

 contains curious tabular inclusions with their long axes nearly 

 parallel to the twin lamellation : see Diersche [30] pi. vii, fig. 3. 



Prof. Lacroix recorded garnetiferous leptynites from the Kandy 

 district, and Dr. Diersche normal and zoisite-bearing granulites. 



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

 the coarsely-banded normal granulites are quarried by means of a 

 short, sloping tunnel. The moonstone (orthoclase without miero- 

 perthitic structure) occurs in rather large individuals in the granulite* 

 Big pieces suitable for cutting are not very abundant, as the 

 cleavage is well developed and the large individuals break into small 

 fragments. The granulite, as seen under the microscope, consists 

 of quartz (elongated and very irregular), and fine-grained, 

 often micrographic ; and very confused intergrowths of orthoclase- 

 microperthite, plagioclase, and quartz. The elongated quartz-grains 

 give to parts of the rock somewhat the appearance of a graphic 

 granite. The appearances presented seem to suggest movement in 

 a nearly consolidated magma, but might conceivably result from 

 the recementing of a crushed quartz-felspar rock. The effect of 

 movement in a viscous magma might be the production of the 

 elongated quartz-grains, and the formation of confused intergrowths 

 from the rest of the magma, the minerals not being able to grow in 

 a well-individualized way after the remixing due to movement in* 

 the viscous mass. The orthoclase-grains are sometimes bordered 

 by a peripheral, more transparent quartz-like zone extending ir- 

 regularly into their interior, and the appearance is often very like 

 that of Lacroix's figure [17] fig. 49, p. 300. Careful exami- 

 nation between crossed nicols, however, shows that the apparent 

 quartz is here generally plagioclase, very faintly twinned, while io. 

 some cases it may be actually quartz. In the latter event the ap- 

 pearance is more conformable with the idea contained in the phrase 



