Julien.] 144 [December 6, 



gneiss, in layers 1 to 6 meters in thickness. This was shown by 

 a cross-section of the beds on the north side of the dunyte deposit 

 at the Jenks Mine, near Franklin, in Macon County. Although 

 the dunyte is thus enclosed in, or interbedded with the horn- 

 blende-gneiss, the latter was never observed to be enveloped by 

 the dunyte. 



Strike. The strike, as shown by the lamination, coincides gen- 

 erally, but by no means always, with that of the associated gneisses. 

 Though often attended by slight curves and even small faults, the 

 plane of lamination usually extends straight and uninterrupted 

 throughout the mass of dunyte. Along the margin of the mass, 

 however, at the ends of the layers wherever visible, a sharp break 

 seems to occur between the dunyte and the gneiss, sometimes 

 with a deviation of the strike of the former, amounting to 20° to 

 30°. To this fact and to the many flexures naturally occurring 

 near the centre of the anticlinal in which the dunyte-beds lie, 

 may be attributed the idea sometimes advanced, that the dunyte 

 is found in erupted dykes. All its characteristics, on the contrary, 

 are simply those of a chrysolite-sandstone, which, wherever unal- 

 tered, and thus without accessory fibrous constituents as a cement 

 or binding-material, is pulverulent and friable. The explanation 

 of these differences in the strike is founded, I think, on the differ- 

 ence in specific gravity of the olivine-mass (3.3) and of the gneiss 

 (2.6), and, it may be, on the greater rigidity of the former. Thus 

 in the course of the plication and contortion of the mass of the 

 gneiss, during its ancient plastic condition, the small enclosed 

 dunyte-masses have sometimes been moved in some degree inde- 

 pendently, and their strike slightly disturbed. 



Weathering. The weathering of dunyte everywhere presents 

 very interesting features : not only in its naked surface and dun 

 color, which render an outcrop of dunyte distinct and desolate to 

 the eye, as far as it can be seen, among the forest-clad mountains 

 of North Carolina, as well as of New Zealand : but also in an 

 extreme ruggedness, due to the irregular projection of laminae 

 and of rough, jagged points — the pitted and honeycombed sur- 

 face being often similar to the fretting of a coral-reef by the surf 

 of a tropical sea. The chemical decomposition, however, is gen- 

 erally more rapid than the disintegration, the resulting ochreous 

 mass being bound together by a network of plates of quartz or 



