giD Count cle Bournon's Description of 
are found in the sand of Ceylon, there are three which deserve 
/ 
notice, because they have not yet been mentioned by any author ; 
these are, a light yellow, like the colour of honey, a beautiful 
clear emerald green, and a red slightly inclining to purple. The 
green variety, which indeed might easily lead to a false idea of 
the stone, is, most probably, what has caused some authors to 
mention the true emerald as being indigenous to Ceylon, where, 
hitherto, no trace of that stone appears to have been met with. 
This error was the more likely to be committed, as it was not 
then known that the regular hexaedral prism, with terminal 
faces perpendicular to the axis, was one of the crystalline forms 
belonging to the tourmalin ; and that tourmalins of a beautiful 
emerald green colour, and perfectly transparent, were sometimes 
met with of that form. I have placed some very pretty small 
crystals of this kind in Mr. Grevillf/s collection. 
The tourmalin of a purplish red colour, found in the sand of 
Ceylon, is exactly similar to that of Siberia, to which the names 
of rubellite , of daourite , and of Siberia, have been successively 
given, and which the Abbe Hauy has ultimately distinguished 
by the name of apyrous tourmalin. Its form is precisely the 
same as that of the tourmalin, properly so called ; nor does the 
measure of its angles exhibit any difference ; especially if that 
measure is taken upon crystals which are of a perfectly deter- 
mined form, and which have not, upon their pyramidal planes, 
any aggregation that can cause a change in the form of those 
planes. I have placed in Mr. Greville’s collection, a small 
group of this kind of tourmalin, from Ceylon, the colour of 
which is a beautiful red ; among its crystals, which have triedral 
pyramids with rhombic planes, may be observed one that has 
a dodeeaedral prism, with its terminal faces perpendicular to its 
