New York Paper - The Abrasive Efficiency of Corundum

In the summer of 1894, a specimen of corundum from Acworth, Ga., which mas reputed to be of markedly inferior quality for the manufacture of corundum-wheels, was received by the Geological Survey of Georgia, with the request that it be analyzed, in order to ascertain whether this inferiority was associated with any peculiarity of composition. In its appearance there was nothing uncommon, though it seemed to be rather easily scratched with a knife, while, at the same time, it scratched agate easily. An analysis gave the following results: Alumina, 94.58; silica, 1.77; magnetic oxide of iron, 0.69; calcium oxide, 0.44; and water, 2.51 per cent. There is nothing unusual in this composition, except the amount of water, which is usually, in southern corundum at least, from 0.3 to about 1 per cent. Concerning this corundum, the Mineral Resources of the United States, 1893, pp. 676 and 677, Bays: "It is supposed that this variety of corundum contains a little water, as it is