16 



JOUKNAL OF THE MiTCHELL SoCIETY 



[June 



and is considered the best corundum ever put on tlie market. 

 There has been no production of corundum from the Southern 

 States since 1904. The credit for the development of the cor- 

 undum mined in North Carolina and Georgia, which resulted 

 in the building up of the corundum industry in this country is 

 due principally to Col. C. W. Jenks and Dr. H. S. Lucas, 

 the former having begun the work at the Corundum Hill Mine 

 in 1871. 



There are many interesting occurrences of corundum in the 

 South and at the present time it is known to occur in the fol- 



lowing rocks: 



Igneous 



Metamorphic 



Alluvial 

 Undetermined 



f Peridotite 

 \ Pyroxnite 

 ] Amphibolite 

 [ Anorthosite 



{Serpentine 

 Gneiss 

 Mica-schist 



] Gravel deposits 



] Emery 



5 Granite 

 \ Pegmatite 



r Quartz-schist 

 \ Amphibole-schist 

 [ Chlorite-schist 



The principal commercial deposits of corundum were asso- 

 ciated with the peridotite rocks and other closely allied basic 

 magnesian rocks, which form a narrow belt 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. 



Corundum in Peridotite : — Throughout nearly the entire 

 southern portion of the belt, 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 serpen- 

 tine. Under the microscope thin sections of the dunite show 

 an alteration to serpentine between the particles of olivine. 



The peridotites and associated basic rocks occur as oval, 

 lenticular, and irregular masses and sheets in a region of meta- 

 morphic rocks composed chiefly of biotite-gneiss. As subordi- 

 nate f acies of this normal gneiss, however, more or less extensive 



