112 SPOLIA ZEYLANICA. 



NOTES. 



1. Uraninite. — This mineral (otherwise kuo wn as pitchblende) 

 is of considerable interest as being the chief source of radium at 

 the present time, associated with other rare elements. The 

 composition is somewhat variable, but the mineral is usually 

 described as a uranate of uranyl, lead, usually thorium (or 

 zirconium), often the metals of the lanthanum and yttrium 

 groups, with the gases nitrogen, helium, and argon in varying 

 amounts ; radium is present in very small quantities. 



A considerable quantity of uraninite in small cubic crystals has 

 been obtained by Mr.X D, Holland in the Balangoda district, but 

 it is not yet known in situ in this area. 



X2 



Crystal of Uraninite from Ambalawa. Gampola. 

 It occurs also at Gampola, where it was found on Ambalawa 

 estate by Mr. G. P. Gaddum. It is here found very sparingly, in 

 lustrous sharp-angled cubic crystals in a pegmatite vein travers- 

 ing granulite. The pegmatite is seen in several boulders on the 

 upper slopes of the Ambalawa estate : the boulders are evidently 

 derived from the hill above. The pegmatite vein consists of quartz, 

 flesh-coloured orthoclase, and biotite (in six-sided crystals), with 

 accessory greenish apatite, black tourmaline, and also uraninite. 

 The uraninite is rather easily recognized by its high specific 

 gravity (exceeding 9*0), black colour, and cubic form. The peg- 

 matite vein does not exceed 14 inches in width, and runs mainly 

 parallel to the foliation planes of the granulites, but sends oflE 

 branches and tongues which cross the foliation and again run 

 along the foliation planes. The minerals are interlocked at the 

 junction, and there is rather a transition from pegmatite to 

 granulite than a sharp junction. In other words the pegmatite, 

 as is often the case in Ceylo-n, has rather the aspect of a segregation 

 vein. This occurrence is of considerable interest, as the mineral 



