174 SPOLIA ZEYLANICA. 



as a gem and used for decorative purposes. A good example, show- 

 ing a star by reflected light, similar to a star sapphire, may be 

 seen in the mineral collection of the Colombo Museum, to which it 

 was presented by Mr. W. C. Wild. Cleaved transparent quartz is 

 found in situ in several places {e.g., near Morawaka) besides the 

 Matale District, forming knots in the granular quartz. Its com- 

 parative scarcity, however, in situ may be attributed to the fact 

 that the surrounding granular quartz disintegrates readily, the 

 homogeneous transparent portion being left intact. 



It is of course possible that cleaved quartz may sometimes arise 

 from the dynamo -metamorphism of pegmatite or infiltration veins, 

 but I have seen no example of this ; the effect of earth movements 

 on small masses of quartz being rather to shatter the mineral than 

 effect any re-arrangement of its particles. Since writing the above 

 I have observed near Naula, 18 miles north of Matale, an occurrence 

 of idiomorphic and hypidiomorphic transparent quartz associated 

 with a pegmatite (gi-aphic granite). The crystals were intergrown, 

 and faces were found as much as 2 ft. long. They were not 

 actually in situ, but the quartz was undoubtedly that of the peg- 

 matite. I am inclined to think that their origin was due to 

 re-cry stalhzation, as near the locality cleaved granular quartz was 

 found, and other rocks near showed clear signs of strong earth 

 movements. 



The series of crystalline schists or gneiss is invaded by intrusive 

 pegmatites, in which the quartz is often intergrown with orthoclase 

 and microperthite, forming graphic granite. The quartz in coarse 

 varieties of these pegmatites may sometimes form masses of 

 considerable size. It is, as a rule, translucent, and is fairly homo- 

 geneous in structure. 



Fine quartz veins also occur filling fissures in the gneiss. These in 

 many cases can be shown to be genetically related to the pegmatites. 

 That they were sometimes injected at a considerable temperature is 

 seen by the iftetamorphism they occasionally produce in the gneiss, 

 invading it, silicifying it, and giving rise to the formation of iron ores 

 (e.g., at Morahela near Balangoda). The quartz of these veins is, as 

 a rule, white, and has a loosely crystalline structure. It often bears 

 hornblende (e.g'. , at Rambuke near Rakwana) , iron ores, especially 

 ilmenite, also tourmaline, which occurs in needles, or is sometimes 

 seen intergrown with the quartz in graphic fashion. A fine example 

 of this curious rock is exhibited in the Mineral Gallery. To be distin - 

 guished from these quartz veins, which are magmatic, or at least 

 solfataric in origin, are the later infiltrations of silica, following rock 

 decomposition, filling fissures and cavities. The quartz may 

 crystallize in idiomorphic forms, and in one observed case, near 

 Rakwana, was amethystine. 



Veins of quartz are often seen associated with basic lenticles in the 

 gneiss. These veins often appear to be the result of crush due to 



