CORUNDUM IN IGNEOUS ROCKS. 41 
Similar to this Canadian occurivnce is the corundnm-anorthite 
rock, described by Doctor Morozewicz," from a locality on the Bar- 
sowka-lviver, in the ITrals, Kussia. The percentage of corundmn in 
these rocks of the Urals seems to oive promise of economic importance. 
CORUNDUM IN NCKITE. 
In the vicinity of Peekskill, Westchester County, N. Y., cornndum 
has been found associated with norites, which have been described 
by Mr. C. H. Williams.^ These rocks belong to the Cortlandt series, 
of which the prevailing rock type is characterized l)y the i)resence of 
the mineral hypersthene. But though this mineral is there so abun- 
dant, a normal norite, containing nothing but plagioclase feldspar 
and hypersthene, is extremely rare. Tliere is more or less "biotite, 
hornblende, or augite developed in nearly all rocks of this class, so 
that there is a gradual transition from normal norite to mica-diorite, 
hornblende-diorite, and gabbro. The intermediate varieties are much 
more common than the extremes, and they have been classified by 
Williams according to the prevailing nonfeldspathic mineral. Where 
hypersthene prevails the rocks are grouped as norites, being sub- 
divided into normal norite, hornblende-norite, mica-norite, and augite- 
norite, according to the presence of these different minerals in the 
rock. These so grade into each other that no sharp line can be 
drawn between them. 
Associated with the norites, 3 and 4 miles southeast of Peekskill, 
N. Y., are deposits of magnetite and emery. These deposits are not 
in a continuous vein, but are more like segregated masses. Attempts 
have been made to work these for l)oth iron and emery, but as iron-ore 
deposits they were soon abandoned. They are still worked to a con- 
siderable extent for emery by the Blue Corundum Mining Company, 
of Boston, Mass.; the Tanite Company, of Stroudsburg, Pa., and 
H. M. Quinn, of Philadelphia, Pa. An examination of the emery ore 
by Messrs. J. D. Dana ^ and G. H. Williams '^ has shown that the 
corundum component is often scattered rather sparingly through the 
ore, and what had formerly been supposed to be green chlorite Avas 
found to be the iron-magnesian spinel, pleonaste. The corundum in 
the emery varies from small colorless g-rains and larger bluish grains 
to crystals 7 mm. in diameter, which show a hexagonal outline. 
The i)leonaste, which is so commonly associated with the emery, 
has been found at the Cruger iron mine, in the eastern part of the 
township, as veins in a nearly normal norite, into which it passes by 
gradual transitions. The most compact specimens of the ore at this 
" Tschermaks mineral, und petr. Mitthei!., vol. 18, heft 1. 
"Am. .Tour. Sci., .3(1 ser., vol. 8:?, 1887, pp. 135, 109. 
. '■ Idem, .3d ser.. vol. 20, 1880, p. 1!)!). 
"Idem, 3d ser., vol. 3.3, 1887, p. 104. 
