BULL. GEOL. SOC. AM. 



VOL. 16, 1904, PL. 76 



Figure 1. — Block from the Serpentine-amphibolite Contact on the Tucker Propekty 



Light colored or left-hand side of the block is serpentine; dark portion amphibolite. 

 Sharpness of line of contact best shown at upper and lower edges 



Figure 2.— Section of cross-fiber Vein 



Fiber at intervals is separated by films and bands of magnetite. Ore-bands may 

 be central or lateral, but are rarely well developed adjacent to the serpentine. They 

 sometimes fill what appears to be a fractured wall or edge of the fiber-band, which in 

 some respects suggests a replacement of the serpentine by the fiber along a line of 

 weakness, and not necessarily the filling of an actual crevice in the rock. 



SERPENTINE BLOCK AND A SECTION OF A CROSS-FIBER VEIN 



