Plate 15 



To face p. 54 



itiili, ni i jtti'iiiliiiilm. iii. 1 liii'!iiiili'i'ilr"iiL; ' i f; iAii'!!'~ t lL- ... 



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1 Sphalerite, .Topi in Mo. 



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2 Millerite, Gap mine, Lancaster c<>. 1'a. 



