1922] A Magnetite-Marble Ore at Lansing, N. C. 147 



The greater part of the country rock is a coarse gray banded gneiss 

 that looks very much like a squeezed porphyritic hornblende granite, 

 perhaps a phase of the Blowing Rock gneiss, also placed by Keith in 

 the archean. This is interlayered with light-colored gneiss which was 

 originally an augitic syenite. It now consists of large anhedrons of a 

 microperthitic feldspar, large light green masses of amphibole, con- 

 taining here and there nuclei of pyroxene, and surrounded by a border 

 of tiny epidote crystals lying in all azimuths. There are also present 

 a small quantity of brown biotite and a few large grains of quartz. 

 The feldspars are crushed around their edges into a fine-grained mass 

 which now consists of quartz, epidote and pale green amphibole. 

 These gneisses are intersected by veins of pegmatite that is almost 

 devoid of dark components, and on the borders of which are large 

 garnets. In many instances the feldspar of the pegmatites is partially 

 changed to epidote as at Cranberry. In a cut on the railroad layers 

 of hornblende schist are in the gneisses, and along these shearing took 

 place with the production of actinolite-asbestos. 



The ore body is sharply marked off from the country rock by the 

 layers of schist below and above. In shape it appears to be irregular. 

 In general it strikes a few degrees E. of North and dips about 36° 

 S. E. In a portion of its course the dip and strike are regular, indi- 

 cating a width of only four feet and in some places the ore is cut out 

 entirely by what appear to be great fragments of the country rock or 

 by small faults. Near the present end of the tunnel the ore body 

 was apparently chimney-like. It was encountered in an old hole on 

 the surface above the tunnel and was followed downward in a small 

 steeply pitching shoot into the present ore body, where it expands into 

 a sheet with the dip and strike of the surrounding gneisses. At the 

 foot wall is a narrow seam of calcite that appears to be secondary as 

 it sends veinlets into the contiguous ore and gneisses. 



In mass the ore appears distinctly schistose. On its borders are 

 selvages of garnet and hornblende, several feet thick. Within these 

 the ore is fairly uniform in character, varying only in the proportions 

 of magnetite and carbonates present. Here and there near its edges 

 are pockets of loose magnetite, especially near the foot wall, where 

 the sparse carbonate cement in lenses of granular magnetite may have 

 been dissolved by percolating water. The pyrite that has already 

 been referred to is confined almost exclusively to the borders of the ore 



