176 SVOlilA ZEYl.ANICA. 



cherts is derived from an organic sonrce, such as sponge spicules 

 and the tests of radiolaria and diatoms. The Ceylon cherts, 

 however, are entirely inorganic in origin, and may be described 

 as silicified rocks. Dr. A. K. Coomaraswamy* has shown that 

 the original rock was, in all the cases he investigated, crystalline 

 limestone, in which the carbonates have been replaced by silica 

 introduced in solution by percolating water. Thin sections of the 

 rock, which commonly occurs in the neighbourhood of crystalline 

 limestone, when examined under the microscope, show that it con- 

 sists of spherulitic aggregates of chalcedony or structureless opal, 

 or both, which may enclose individuals of plilogopite, graphite, and 

 spinel, characteristic minerals in crystalline limestones. In one case 

 corroded dolomite crystals were observed. It was doubtful at the 

 time of Dr. Coomaraswamy's observations if these silicified rocks 

 could originate except from limestones, but since then similar rocks 

 have been found {e.g., near Dodanduwa) which are far from any 

 exposures of limestone, and bear unmistakable evidence in the form 

 of decomposed felspar individuals of their origin from some siliceous 

 rock by decomposition and silicification. The cherts are most 

 commonly shades of bro\vn and red, but are also white and green. 

 The green varieties consist principally of opal, and are softer than 

 the brown. Brown chert was formerly worked for gun flints and 

 strike-a-lights, and is known in Sinhalese as gonapitta or ginigala. 



Pebbles stained brown with iron oxide, and wholly or partly 

 siliceous, are often dredged up in gemming operations from the beds 

 of rivers, and are known as kahdnda. They appear to be water- worn 

 pieces of orthoclase or micropegmatite which have been decomposed 

 and silicified. 



It is hoped that these notes on the difiFerent forms of quartz in 

 Ceylon, and their modes of origin, may be some guide to local 

 collectors of stone implements in forming an opinion as to the nature 

 and probable source of the material used for implements or brought 

 from rock or stream for purposes of ornament. 



Implements of white quartz have been found in South Africa 

 and elsewhere, but those of clear vitreous quartz are of extreme 

 rarity in all other parts of the world, except Ceylon, where it was the 

 chief material used, and where implements of that material are found 

 in abundance in certain localities. 



For the manufacture of implements the transparent cleaved quartz, 

 which has been shown to be of metamorphic origin, was admirably 

 adapted, as it split naturally into more or less fiat flakes which could 

 be easily worked to an edge. Implements showing a cleavage face 

 or fractures are common. Crystals were also worked. The white 

 translucent forms of quartz do not appear to have found so 

 much favour among the ancient artificers in Ceylon, but this may 



* Geological Magazine, Decade V., Vol. I., 1904, pp. 16-19. 



