318 Count de Bournon's Description oj 
and the pyramidal planes of which, in the only extremity of 
the crystal that remains, are situated upon the edges of the 
prism. 
Ceylanite. The stone called Ceylanite, by Mr. La Metherie, 
who is the first author that has considered it as a particular and 
distinct species, (distinguished by the name of pleonaste , in the 
Mineralogy of the Abbe Hauy,) is also sometimes .found in the 
sand of Ceylon ; it is, however, in general, by no means com- 
mon. Of the crystals of this substance that I have collected 
from this sand, many are perfectly transparent; a character 
which appears to have been hitherto unobserved in it. Its 
colours are very various. Besides black and green, which have 
already been mentioned by authors, I have seen it of a reddish 
or flesh colour, with a yellowish cast; of a fine bluish green, 
like the aqua marine ; and of a fine sky blue, rather pale. When 
the Ceylanite is of the last-mentioned colour, whether it be a frag- 
ment or a flattened octaedron, it might very easily be mistaken 
for a sapphire. Its most usual colour is a brownish green. 
As this substance has, in all its external characters, a striking 
resemblance to the spinelle, of which it is perhaps only a species, 
I think I cannot be too particular in pointing out those cha- 
racters which may in some measure serve to distinguish it ; I 
shall therefore add, that its hardness is rather inferior to that of the 
spinelle, the Ceylanite being scratched by the spinelle, while the 
latter cannot be scratched by the Ceylanite ; also, that it usually 
exhibits, by irregular striae, parallel to the edges of the regular 
calls isogone,) may be met within this substance,, in order to determine its nature. 
He will no doubt feel satis: action in hearing, that there exists, in the collection of Sir 
John St. Aubyn, a small detached crystal of this substance, of a fine red colour, 
which has exactly the above-mentioned form. This crystal I found in the sand of Ceylon, 
