PLATE Xni 



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Fig. 1. Volcanic glass from sample 17; light-colored 

 clustered and individual phenocrysts of basic plagio- 

 clase feldspar, surrounded by reaction rims; dark- 

 colored crystals and microlites of augite and olivine; 

 plane polarized light (x ca. 50) 



Fig. 2. Manganese -palagonite nodule from sample 57; 

 showing alteration of light -colored spherulites of 

 volcanic glass to darker palagonite, usually surround- 

 ed by manganese and often replaced by it; note isolated 

 fragments of spherulites in black manganese coating, 

 laminar distribution of manganese, and relatively 

 clear rectangular phenocrysts of feldspar, in palagonite; 

 plane polarized light (x ca. 20) 



