the Corundum Stone , and its Varieties, Sec. 289 
here spoken of are chatoyant ; and, in the fragments, the planes 
which correspond to these faces have a similar property, when 
held in a proper direction. In some, these faces then appear of 
a peany white colour ; in others, the colour is rather yellowish : 
some of them reflect a pale blue colour ; in many others, the 
coloiii reflected is a beautiful deep sapphire blue, that entirely 
occupies the whole extent of the face which possesses the pro- 
perty here spoken of. To this stone ought to be referred, that 
which is known by the name of moon-stone of Ceylon, when it 
is not 01 the kind called cimophane, (the chrysoberyl of Werner,) 
which is often found also in the sand of this island, mixed with 
rubies, sapphires, &c. 
-Tne opinion I am naturally led to adopt, in consequence 
of the detail I have just given respecting this stone, is, that 
it most prooably is a kind of felspar, and ought to be ranged 
with that substance, as forming an additional variety. 
In some of the pieces of this stone, which are found in the 
same matrix with the imperfect corundum of the Carnatic, a 
talcy earth (which often also appears in a separate state) is in- 
terspersed throughout their substance, and causes them to have 
a less compact texture, and a very inferior degree of hardness - . 
The stone, at the same time, acquires a slight greasiness to the 
touch, and loses the semi-transparency which is peculiar to it : 
it may still, however, be easily divided, in the direction already 
descrioed as that in which it is naturally divisible.. 
Fibrohte. 1 he substance I have distinguished by this name, 
which sometimes also accompanies the imperfect corundum from: 
the Carnatic, in its matrix, has always offered itself to my obser- 
vation, either of a white colour, or of a dirty gray. Its hardness 
appeared to me to be rather superior to that of quartz ; as, after 
