RED MOUNTAIN, ARIZONA 139 



were a relatively late contribution to the cone, and are unconsoli- 

 dated. Within the mountain the fragmental material is cemented 

 into a typical volcanic tuff. When seen from a distance, the color of 



Fig. I. — A topographic sketch of Red Mountain, Arizona, with the directions of 

 dip and strike plotted at several points. 



the tuff resembles that of the red beds, but at close range it is seen 

 to be a combination of yellows and browns. 



The angular blocks, which range up to 4 feet in diameter, 

 are composed of a dark-red porphyritic andesite. The phenocrysts 

 are labradorite feldspars, pyroxenes, hornblendes, and magnetites. 

 The lava flow and agglomerate are exposed only on the southwest 

 side of the mountain, about 100 feet below the summit. The largest 

 out-crop shows a zone, 10 feet thick, of compact lava in which there 



