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Corundum Stone from Asia. 415 
These are the circumstances connected with the strata worth 
mentioning. The examination of Corundum on which our 
present knowledge rests, is nearly that which an Indian mine- 
ralogist might derive of the history of feldspar, from a lump of 
Aberdeen granite, out of one or two different quarries. He 
might ascertain a few modifications of the crystal of feldspar, 
its fracture, and matrix ; but he would have no knowledge of 
the. purest or more beautiful sorts which other quarries produce, 
in Scotland, at Baveno, at St. Gothard, and in Auvergne. I there- 
fore think it essential to mention, that Corundum, under cir- 
cumstances favourable to its crystallization, becomes glassy in 
its fracture, and of various colours. I have not only observed, 
in crystals of Corundum, specks of a fine ruby colour, but I 
have fragments of crystals, in texture and every respect like 
the colourless Corundum, of a fine red colour. It is cer- 
tain that we obtain from India, Corundum which may pass 
for rubies. I have sent to India some of the Corundum with 
small ruby specks, which were not sufficiently distinct or large 
either for measurement or analysis, in hopes of being enabled 
to ascertain correctly the form of Salarn rubies found in Co- 
rundum ; in the mean time, I have the Corundum of a fine red 
colour. Looking over some polished rubies from India, I se- 
lected one which appeared laminated like Corundum, and had 
also the chatoyant or play of light on its laminae:, which formed 
an angle in the stone. The lapidary called it an Oriental 
ruby. I altered the form of the cutting, so fortunately, that 
the reflected rays formed a perfect star; a phasnomenon I 
had observed in the sapphire, and expected in Corundum, 
but not in the octoedral ruby. The specific gravity of 
