Vol. 56.] CEYLON ROCKS AND GRAPHITE. 601 



specimen was found to contain chiefly microcline and quartz, with 

 also a little plagioclase, biotite, muscovite, and calcite. 



Similar rocks with a little pyroxene and hornblende occur in the 

 shallow road-metal quarry, by the roadside north of the village. 

 Typical microcline-gneiss occurs near the fork in the road some 

 miles north of Dambulla, and also near the new Sigiri rest-house, 

 where the mineral-banding is very conspicuous. 



Other exposures were noted on the Anuradhapura road at distances 

 of 51 j, 52|, and 72J miles from Kandy. 



(10) Anorthosite-Gneiss. 1 



Certain gneisses found in Ceylon come under this head, inasmuch 

 as the sole or dominant felspar is plagioclase. 



Sigiri. — The imposing Sigiri rock is well known from an 

 archaeological point of view, and has been rendered accessible by 

 Mr. Bell. It is a large rounded mass of gneiss, overhanging more 

 or less on every side. The gneiss is conspicuously banded. Dark 

 vertical surface-stains are evident, as is generally the case with the 

 bare rocky slopes that occur in Ceylon. Thin slices show quartz 

 and plagioclase, with more or less biotite, and a little secondary 

 muscovite. 



Colombo. — From quarries in the Madampitiya and College roads 

 several specimens were obtained, and six microscope-sections prepared. 

 The minerals are quartz, orthoclase, plagioclase, biotite, hypersthene, 

 magnetite, apatite, and zircon. The term anorthosite-gneiss 

 is applicable to those varieties which consist chiefly of quartz and 

 plagioclase, with a little biotite and hypersthene. In specimens 

 from the College-road quarry minute quantities of spinel are 

 associated with the magnetite, as is the case in the rock from the 

 site of the new graving-dock (p. 595). 



Kalawewa. — A specimen from near the big sluice shows in a 

 microscope-section plagioclase (17° 17°, probably oligoclase), quartz, 

 hornblende, augite, biotite, magnetite, apatite, and sphene. 



(11) Granite. 



The curious i animal-shaped ' hills in the Kurunegala district 

 were described by Dr. Diersche as granite. He says also that the 

 columns of the Brazen Palace at Anuradhapura are hewn granite. 



At Mahara, a large convict-quarry in the Colombo District, a 

 great depth of rock is exposed ; it is overlain by laterite. The rock 

 is best described as a rather variable gneissose granite. It is sent 

 in large quantities to Colombo, where it is crushed and mixed with 

 cement, and moulded into large blocks, which are used in the 

 construction of the new breakwater. 



1 The term gneiss is used for convenience, here and elsewhere, though it is 

 perhaps hardly correct to speak of igneous rocks as gneisses. 



