generally flesh-coloured, but sometimes white, having a thickness of from one-fourth to oneeighth inch. When a corundum crystal has been broken out or has dropped out from the rock, the place where it lay can always be distinctly recognized by this shell which remains behind. Microscopic examination shows that this shell differs from the remainder of the matrix in the absence of minute corundums, sillimanite and most of the accessory minerals.

"It is clear from the map that the outcrops of the rock in which corundum occurs lie in successive lines, roughly parallel to the strike of the gneiss, namely, N.N.E.-S.S. W.

This conclusion has since been confirmed by the discovery of corundum occurring under precisely similar conditions in the Hosur taluk to the north, and also in the same line to the south, making the corundumbearing band over 24 miles long. This fact, and the circumstance that the mineral occurs in two and probably more parallel bands of slightly different rocks, make the Paparapatti area a decidedly promising one. Experiments to test the prospect of mining for corundum along this band have been conducted by Mr. C. S. Middlemiss, on a lenticle 13 x 8 x 9 feet, near the village of Erranhalli, 2 miles s. w. by s. of Palakod. It was found that 722 cwt. of matrix-rock yielded 2,845 lb. or nearly 3.5 per cent. of pure corundum, at a cost of R 385-2-0, that is at 8 annas per cwt. of rock broken up and 3.9 lb. of corundum cleaned. 15 As the chief expense was incurred by the mere labor of crushing the rock, which was done entirely by hand, it is certain that the cost of extracting the corundum would be greatly reduced if stone crushing and washing machinery had been employed, as of course would be the case in actual mining operations on a large scale." Relative Richness of Ontario and India Deposits. Since Mr. Holland-who is in a good position to judge on account of the fact that more work has been done on corundum Advantages in India than in any other country Ontario -considers the area just described a decidedly promising one, I have

of the

Corundum.

15 8 annas about 11 cents. The cleaned corundum therefore cost 2.82 cents per pound.

thought it well to quote his description fully, both as to the characteristics of the mineral itself and as to its mode of occurrence, so that comparison might be instituted between these deposits and those of Ontario.

Since in order to work either the India or Ontario deposits on a large scale would require the use of machinery, the cost of mining and crushing the rock in the two countries may be taken as being practically the same. In so far as climatic influences, transportation facilities, water for washing the crushed material and for use in generating power, electric or otherwise, are concerned, the Ontario deposits are certainly as well situated as any in the world.

The chief constituent in the India rock, as in that of Ontario, is felspar. But in addition to the felspar the India rock contains often a considerable proportion of fibrolite, rutile and spinel. These minerals are heavier than felspar and have specific gravities of, respectively, 3.23 to 3.24, 4.18 to 5.2. 3.5 to 4.1, that of the felspar being 2.57. On washing away the felspar these minerals would tend to come down with the corundum, which has a specific gravity of 3.95 to 4.10. and would thus give an impure product. Mica occurs in the rock from both districts, and hence this mineral may be left out of consideration in making a comparison of the treatment of the two. The heavy mineral which comes down with the Ontario corundum on washing is magnetite, but this mineral is easily and cheaply isolated by passing the mixture over

a magnetic separator. Moreover the magnetite, which averages about four per cent. of the rock treated and is of good quality, is in itself a by-product of value for use as an iron ore.

In the mill tests of the Hastings rock made last year by Prof. DeKalb, the corundum obtained from one sample of 550 lb. represented 12.74 per cent., and in another sample of 1250 lb. the corundum separated was 15.50 per cent. of the rock treated. 16 Since the India rocks yielded only 3.5 per cent. of pure corundum, the Ontario deposits would seem to have a considerable advantage over 16 Seventh Report Bureau of Mines, p. 246.