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THOMAS L. WATSON 



salts through the rock. Why the definite arrangement into long 

 pencils and dendritic forms manifested megascopically, evidence is 

 again lacking, for the textural relations of the minerals in the dis- 

 colored areas are precisely the same microscopically, as for other 

 portions of the rock. The character of the staining suggests that the 

 spotted and streaked appearance of the rock is a superficial phenome- 

 non, and perhaps does not extend to any very great depth. 



Fig. 4. — View showing weathered surface of the rock. Partial leaching of the 

 dark spots is emphasized in the upper portion of the picture. Photographed from 

 hand specimen. (One-half natural size.) 



CHEMICAL COMPOSITION. 



The chemical composition of the rock is given in analysis I of 

 the table of analyses. The analysis of leopardite was made by Dr. 

 F. A. Genth from the freshest fragments of the groundmass obtain- 

 able. The most striking features of the analysis are (i) the very acid 

 character of the rock, as manifested in the high SiOg content; (2) 

 the nea-rly complete absence of CaO and MgO ; and (3) the increased 

 NagO which is in excess of the KgO. The analysis, however, har- 



