CRYSTALLINE ROCKS OF CEYLON. 109 



granulites, and the stiil smaller quantity of other rocks possibly 

 of a metamorphosed sedimentary character, the frequent oc- 

 currence in the limestones of fragments of peripherally modified 

 granulite, and the strong general similarity between the characters 

 of the crystallized limestones and those of igneous foliated 

 crystalline rocks. 



Putting aside, however, the doubtful question of origin, it 

 is clear that as far as their present characters are concerned 

 the crystalline limestones are contemporaneous with the granu- 

 lites ; and there can be little doubt that they existed in a state 

 akin to fusion at the time of the consolidation of the latter, 

 and that their accessory minerals crystallized under conditions 

 resembling those accompanying the cooling of such plutonic 

 magmas as have for example given rise to the granulites 

 themselves. The foliation of the limestones must have been 

 acquired at the same time and in the same way as that of the 

 granulites. 



A group in some respects intermediate between the limestones 

 and granulites includes rocks composed essentially of one or more 

 of the minerals diopside, mica (phlogopite,&c.), amphibole, scapoiite, 

 spinel, sphene, and calcite, with more rarely felspars, ini^rcasite, 

 serendibite, &c. In these rocks the silicates are usually idiomor- 

 phic when moulded 1)y carbonates. Of the minerals mentioned 

 diopside and mica are predominant. The rocks occur (a) as 

 junction rocks between limestone and granulite, {h) as inclusions 

 in the limestones, (c) as dykes in the granulites, these dykes 

 being usually narrow and having a zoned structure, and (d) as bands 

 of rock interbedded with the granulites. Mica of commercial value 

 may occur in rocks of this type. The bands rarely exceed 6 ft. in 

 thickness and are often narrow. Continuity between the types 

 (c) and (d) can sometimes be observed. Some of the types of rock 

 included here are very haiulsome, especially the coarse varieties 

 in which scapoiite is conspicuous. 



Rocks of the Galle groiip are also in some respects intermediate 

 between the limestones and granulites, inasmuch as they contain 

 numerous lime silicate minerals and differ in other resi)ects from 

 the typical granulites, although in many waj^s resembling them ; 

 the presence of wollastonite (not yet found elsewhere in Ceylon) 

 and of scapoiite and sphene (in addition to a green pyroxene 

 and the quartz and felspars characteristic of ihe granulites' and 

 absence of garnet, amphibole, and mica are distinguishing characters 

 of the Galle rocks. As in the granulites, there is a wide range 

 of types, from basic to acid, and mineral banding is very conspi- 

 cuous (fig. 2). 



