CORUNDUM IN METAMOEPHIC ROCKS. 53 
eastern border of this mass are corundiini bearing for a thickness of 
about () feet. The corundum occurs in small grains and is not 
abundant. 
Near the confidence of Owens and Parker creeks, Avhich form West 
Fork of French Broad River, in Transylvania County, N. C., several 
large bowlders of cyanite have been found on the surface which bear 
grains and small crystals of a deep sapphire-blue corundum. The 
rocks of the vicinity are gneisses, and these are undoubtedly the 
source of these cyanite-corundum aggregates. 
CORUNDUM IN METAMORPHOSED ZONE BETWEEN HARZBURGITE AND GNEISS. 
An important variation from the usual mode of occurrence of 
corundum with the peridotites in the southern portion of the United 
States is found near Pelham, Mass. At the asbestos quarry near 
Pelham there is a lenticular mass of the harzburgite (saxonite) 
variety of the peridotite rocks about 40 feet in width of outcrop and 
200 feet in length, penetrating the acid gneiss of the country. The 
harzburgite is very much altered to a depth of 3 to 12 feet, when the 
hard, nearly fresh rock is encountered, Avhich is of a dull black color 
and is made up of grains of olivine and the orthorhombic pyroxene, 
bronzite. The black color of the rock is due to disseminated particles 
of chromite and magnetite. Part of the magnetite may be due to an 
alteration of the grains of olivine similar to that observed in the 
dunites of North Carolina, where, at the beginning of its alteration, 
there is a deposition of magnetite in fine grains, which forms a net- 
work of black lines often outlining the grains of olivine. 
Professor Emerson has made a petrographical examination of this 
rock and describes it as follows : « 
This is a very fresh mixture of olivine and enstatite, both dusted throu,i?h with 
black ore, largely chromite. It is a dull-black rock of very great toughness. 
The olivine grains have often many crystalline faces. The enstatite is in rare, 
small plates, with parallel sides and irregular ends, and with a fine wavy lami- 
nation, which is often marked by lines of black ore, generally concentrated in 
some part of the plate, especially the center. Although nearly colorless or pale 
bronzy in common light, it has marked pleochroism. It is plainly rhombic, and 
grades into the asbestiform decomposition product in veins running through the 
section. 
None of the anthophyllite that is so abundant in the decomposed 
portion of the harzburgite was observed in the fresh rock. 
From the fresh rock to the surface and the contact with the gneiss 
the harzburgite is more or less completely altered, and penetrating 
through it there is a network of veins of anthophyllite, which are 
more or less asbestiform. These veins vary in width from very thin 
« Mon, U. S. Geol. Survey, vol. 29, p. 52. 
