PLATE XII. 



A. Vein quartz, Banner mine, California. Showing shattering of black argillite by quartz seams; 



pyrite developing in the argillite but not in the quartz; further, brownish (weathered) carbonate 

 deposited next to the argillite in the seams. Beginning of metasomatic alteration apparent by 

 bleaching of the black argillite. After Lindgren. 



B. Secondary galena and blende in ores from Missouri. After Bain. 



