Explanation <>f Plate 7. 



Figure 1. — Litchfieldite in natural light. The dark mineral is lepidomelane. The 

 large gray areas in the lower left of the picture and the light areas 

 surrounded by the mica are eleolite. Everything else is albite. 



.66. 



Figure 2. — Litchfieldite under crossed nicols. Here the eleolite is easily distin- 

 guished from the plagioclase, since the former polarizes with a uni- 

 formly dark gray tint. Nearly all of the material included between 

 plates of the lepidomelane are thus seen to be this mineral. The 

 very light colored aggregate in figure 1 breaks up, under crossed 

 nicols, into a mosaic of small plagioclase grains, that surrounds the 

 basic elements of the rock and separates them from each other. 

 X .33. 



(262) 



