28 CORUNDUM, ITS OCCURRENCE A^TD DISTRIBUTION. 
origin of corundum. The descriptions are taken up in the following 
order: Modes of occurrence in the United States and occurrences not 
found in the United States. 
At the present time corundum is known to occur in the United 
States in the following rocks, descriptions of whicli follow in the 
order given in the subjoined list : 
ConunJiiiii-heariHf/ rods in Tnitcd- Htatcfi. 
Igneous . 
Metamorphic. 
Peridotite. Norite, r Granite. 
Pyroxenite. Plnmasite. \ Syenite. 
Amphibolite. Andesite. I Pegmatite. 
Anorthosite. [Monchiquite. 
Serpentine, r Quartz-schist. 
Gneiss. \ Amphibole-schist. 
Mica-schist, i Chlorite-schist. 
Crystalline limestone. 
Alluvial Gravel deposits. 
Undetermined Emery. 
CORUNDUM IN IGNEOUS ROCKS. 
CORUNDUM IN PP^RIDOTTTE.'^' 
Extending from Tallapoosa County in east-central Alabama into 
the Gaspe Peninsula on the Gulf of St. Lawrence, a distance of more 
than 1,600 miles, there is a narrow belt of disconnected outcrops of 
peridotites and closely allied basic magnesian rocks, which cut the 
ancient crystalline belt of eastern North America. These l)asic rocks 
can be traced north more or less continuously to near Trenton, N. J., 
where the crystalline rocks pass under the younger formations. The 
crystalline rocks again make their appearance south of Hobokcn, 
N. J., and at this place and on Staten Island there are large masses 
of serpentine. Many other outcrops of serpentine, and in some cases 
of unaltered peridotites, have been observed in Connecticut and 
Massachusetts, but it is not until central Vermont is reached that tlie 
belt again forms a more continuous line, and then continues through 
southeastern Quebec into ihe, Gaspe Peninsula. The large areas of 
serpentine tliat are known to exist in the western part of the island 
of Newfoundland extend the belt al)Out 400 miles farther. 
Throughout nearly the entire southern portion of the l)elt, in 
North Carolina, Georgia, and Alabama, the peridotite rocks show a 
freshness almost to the surface of the exposures, and there are few 
localities where there is any considerable area of peridotite entirely 
altered to serpentine. Under the microscope thin sections of the 
dunite show an alteration to serpentine between the particles of 
« Corundum and the peridotite of western Nortli Carolina : North Carolina Geol, Sur- 
vey, vol. 1, 1905. 
