Bulletin of the United States Geological Survey-Corundum and Its Occurrence and Distribution in the United States (A Revised and Enlarged Edition of Bulletin No.180) (1906) (14782217385)

Identifier: bulletinofunited269prat (find matches)
Title: Bulletin of the United States Geological Survey--Corundum and Its Occurrence and Distribution in the United States (A Revised and Enlarged Edition of Bulletin No.180)
Year: 1906 (1900s)
Authors: Pratt, Joseph Hyde
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Contributing Library: Clemson University Libraries
Digitizing Sponsor: LYRASIS Members and Sloan Foundation



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and on Staten Island there are large massesof serpentine. Many other outcrops of serpentine, and in some casesof unaltered peridotites, have been observed in Connecticut andMassachusetts, but it is not until central Vermont is reached that tliebelt again forms a more continuous line, and then continues throughsoutheastern Quebec into ihe, Gaspe Peninsula. The large areas ofserpentine tliat are known to exist in the western part of the islandof Newfoundland extend the belt al)Out 400 miles farther. Throughout nearly the entire southern portion of the l)elt, inNorth Carolina, Georgia, and Alabama, the peridotite rocks show afreshness almost to the surface of the exposures, and there are fewlocalities where there is any considerable area of peridotite entirelyaltered to serpentine. Under the microscope thin sections of thedunite 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.
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CORUNDUM IN IGNEOUS ROCKS. 29 olivine. These peridotite rocks have Ikhmi shown to be of igneousorigin/* The bhint lenticular fcuui in which they are found wouldhe difficult to associate with any origin l)iit that of an intruded igne-ous mass, which Avould also account for f\\i\ ap()))hyses that have beenobserved extending into the inclosing gneiss. At AVebster, JacksonCounty, N. C, a large block of gneiss is completely inclosed by the))eridotites in such a mannc^r as could be attributed only to the intru-sion of the latter Avhile in a molten condition. The line of separationof the peridotites and the gneisses is always sharp, and there is notransitional zone from the acid gneiss to the basic peridotite. Underthe microscope the latter rock shoAvs the granular structure character-istic of plutonic origin, the grains fitting 2)erfectly into one anotherwithout cementing materiaL Associated with all these peridotites is the mineral chromite, whichoccurs as disseminated particles near the b