the Peridotites in North Carolina. 57 



black massive spinel. In thin splinters the spinel is of a very 

 handsome emerald-green color. The masses of the corundum 

 and spinel are partially surrounded by a deep green chlorite ; 

 which latter has also in places been developed in small green- 

 ish scales, between the corundum and spinel ; though the con- 

 tact of the spinel and of the corundum is usually sharp and 

 distinct, showing no sign of alteration. The presence of minute 

 scales of greenish chlorite occur still more rarely in the corun- 

 dum and spinel near the junction of these minerals with the 

 external mass of the chlorite. All the massive corundum 

 shows the characteristic parting lines ; and the spinel shows 

 distinctly the conchoidal fracture. 



A massive, coarsely to finely granular spinel is found at the 

 Corundum Hill mine, Macon County, which has disseminated 

 through it small grains and fragments of pink and white 

 corundum. The spinel and corundum are closely associated 

 with chlorite, which is here more generally developed between 

 the corundum and spinel and in the spinel (between the 

 granules) than it was at the Carter mine. The spinel in the 

 mass appears black, but in small splinters it shows a green 

 color. 



The corundum is found in the dunite in two different rela- 

 tions, one in the zone of alteration products developed at the 

 contact of the dunite and the gneiss, and the other in a similar 

 zone of alteration products, but which are bounded on both 

 sides by the dunite. For convenience, the occurrence of the 

 corundum in these alteration products between the dunite and 

 the gneiss will be designated as a contact-vein and the other as 

 a dunite-vein. The bounding walls of a dunite- vein are not 

 necessarily of dunite ; but may be of serpentine, the common 

 alteration product of this mineral. 



Where the corundum is found in the contact-vein, the fol- 

 lowing sequence is usually observed in a cross-section extend- 

 ing from the gneiss to the unaltered dunite : 



a. Gneiss, hornblendic or micaceous, apparently unaltered. 



b. Gneiss with same general appearance as a, but so decayed that 



the particles readily separate from each other. 



c. Yellowish vermiculites, varying considerably in thickness, with 



a maximum of 6 or 8 inches, and in places entirely absent, 

 so that b comes directly in contact with d. Where present, 

 c often merges into d. 



d. Green chlorite, varying in thickness much like c, and absent 



entirely in places. 



e. Chlorite and corundum. Sometimes with a little vermiculite. 



In places this mass may be largely of corundum, and it is 

 what is called the "corundum vein," varying in thickness 

 from a few inches to 12 or 15 feet. 



