No. 4.-1848.] 



CEYLON1TE. 



97 



ON CEYLONITE FOUND NEAR TR1NCOMALEE. 

 By Lieutenant Hendekson, C.R.R. 

 (Read February 24, 1849.) 



Ceylonite, so called from having been first discovered m 

 Ceylon, is, in its primitive and usual form, a regular octo- 

 hedron. It, however, also occurs as a cuneiform octohedron^ 

 and has been found, though more rarely, in roiled grains. 



In size it reaches from eight to ten carats. The planes 

 of its crystals are smooth, shining, and possessing a vitreous 

 lustre. Its structure is lamellar, and its fracture what may 

 be termed flat conchoidal. Occasionally it has been found 

 to be imperfectly foliated. 



Its specific gravity ranges from 3*6 to 3-7. The lighter 

 coloured varieties (which I have not seen) are said to be 

 transparent. The darker specimens can scarcely be called 

 semi-transparent. On the edges of the crystals they are 

 translucent. It is singly refractive ; in hardness superior to 

 quartz, but inferior to Oriental ruby or spinelle. 



Subjected to the blow-pipe it is found to be infusible, 

 without addition. 



Its component parts are : — 



Alumine ... 68 



Magnesia ••• ... 12 



Silex ... ... 2 



Oxide of Iron ... 16 



98 (loss 2). 



Ceylonite, otherwise called Pleonaste, has, since its dis- 

 covery in Ceylon, been met with also in Norway. It is of 

 the same family as the ruby, but more closely allied to that 

 variety termed spinelle. This latter, indeed, which with 



