EXPLANATION OF PLATES 

 PLATE L 



Figure 12. Section of Ballou Pipe. 



The photograph shows a block cut from the pipe through its center 

 about parallel to its axis (face marked A) and also across the axis (side 

 marked B). The diameter is a httle more than three feet. The concentra- 

 tion of dark sihcates about the margin is very strong. The graphic-granite 

 zone can hardly be distinguished from the main zone of pegmatite. The 

 long dark prisms, more abundant toward the center, are of aegirite-riebeckite. 

 The dark gray center is largely quartz. An indistinct radial structure may 

 be seen. 



Figure 13. 



This is a part section across a portion of one of the Fallon quarry 

 pipes. It was cut from a loose block and its exact location cannot be told. 

 The height of the block is about three feet, but as the section is cut some- 

 what obliquely the actual width of the zones is less than that shown by the 

 figure. D is a piece of the quartz center. C is the zone of coarse pegmatite 

 with its large aegirite-riebeckite prisms. B shows the graphic-granite band, 

 here very strongly developed. A is the marginal zone with a slight con- 

 centration of dark silicates along the inner margin. This band here is very 

 similar to the granite and probably merges gradually into it. 



Compare with Figure 1, page 133. 



