90 CORUNDUM IN THE UNITED STATES. [bull. 180. 
and in parts has a gneissoid structure, and these portions carry the 
corundum. The corundum varies from a deep purplish brown to a 
dark greenish gray, and is in irregular nodules varying from a quarter 
of an inch to an inch in diameter and in elongated barrel-shaped crys- 
tals sometimes an inch long. 
There are two and perhaps more of these corundum-bearing bands 
that are parallel to each other, making the total length of corundum- 
bearing rock that is known over 24 miles. The percentage of corun- 
dum in the rock is very low, experiments that have been made on 
samples taken at different points on the band showing the presence 
of only 3.5 per cent. 
Most of the outcrops of the bands of corundum rock have been found 
in connection with gneiss, and lie in lines that are roughly parallel to 
the strike of the gneiss. Some of them are, however, in close prox- 
imity to a nepheline-syenite. 
Specimens of corundum sent by Dr. T. L. Walker from a district 
about 250 miles north of Calcutta and labeled Pipra, South liewah, 
India, are apparently similar to those described by Holland. The 
corundum is very fine grained in appearance and in nodules up to 
2 or more inches long by 1 or more inches broad, with a pinkish to 
purplish-brown color. These nodules are partially or completely sur- 
rounded by a greenish mica, whose folia are small and rather brittle, 
and which has been referred by Mallet 1 to theeuphyllite variety. In 
the mica there are small rough crystals of tourmaline. Just what the 
occurrence of this corundum is I do not know, but from the general 
appearance of the specimens it should make an ore from which the 
corundum could be readily separated and a very clean product 
obtained. If the corundum in the rock was 10 to 15 per cent of the 
amount required to be removed in mining, this should make a very 
important and profitable corundum deposit. A limited amount of this 
corundum is now being imported by the Norton Emery Wheel Com- 
pany, of Worcester, Mass., and is used in the manufacture of their 
India oilstones. 
In other specimens labeled Salbanni, 4 miles east southeast of 
Barampur, Manbhoorn district, India, there are blue crystals of 
corundum with a rough hexagonal prism embedded in a mass of inter- 
locking bladed crystals of cyanite. 
It is very probable that nearly all of the corundum deposits that 
are known in India are secondary minerals and the result of meta- 
morphism. Professor Judd, in his paper on the Rubies of Burma and 
associated Minerals, 2 says that all the corundum-bearing rocks in 
the districts of Southern Asia appear to be gneisses that sometimes 
pass into schists and frequently contain masses of limestone and 
dolomite. 
1 Min. India, 1887, p. 130, and Dana's Min., 6th edition, 1892, p. 624. 
2 Trans. Royal Soc, London, 1896, p. 191. 
