the Corundum Stone , and its Varieties, & c. 245 
(which I shall in future distinguish by the name of imperfect 
corundum,) has, in general, very little brilliancy; but, in pro- 
portion as the crystals announce, by their greater transparency, 
a greater degree of purity and perfection, their colour becomes 
more lively and more brilliant; this, however, seldom happens, 
except in crystals of a small size. The colour of these crystals 
is various, and seems to depend very much upon the place 
where they are found. In the Carnatic, the prevailing colour 
is a grayish white; which, however, very often approaches 
to a pale green, and sometimes to a yellowish cast. They are 
also found, but much more rarely, of a red, and of a blue co- 
lour; and, when they are of those colours, the red always 
inclines to the purple, and the blue is of that azure kind which 
is generally known by the name of sapphire blue. In the corun- 
dum of China, and in that of the kingdom of Ava, the colour 
is generally a green, more or less deep, with a dull appear- 
ance ; or it is brown. The corundum of the coast of Malabar, 
appears of a reddish brown in those parts which are opaque; 
but, whenever there is, in any part of it, the smallest degree 
of transparency, the forementioned colour always appears to be 
accompanied by a tinge of purple. 
In the perfect corundum, which is found in Pegu and in 
Ceylon, but which is now most commonly brought (when in 
its natural or unpolished state) from the last mentioned place, 
the colours are much more various, and more lively. The chief 
of these colours are, red, blue, and yellow. The red colour con- 
stitutes the stone known by the name of oriental ruby ; but it 
seldom happens that this colour has not a small mixtureof blue, 
which gives it a tinge slightly inclining to purple. The blue 
colour is always that which is known by the name of azure 
