248 FINLAY 



2. Analcite Tinguaite 282 



a. Mt. Armadillos Type 282 



l>. Corona Type.. 283 



Analysis by Dr. H. S. Washington. Calculations 285 



3. Camptonite 285 



a. San Carlos Type 285 



b. Casa Grande Type 287 



c. Rincon Type 289 



Analysis. Calculations 289 



4. Vogesite 290 



5. Limburgite 291 



VII. Chemical Relations of the San Jose Rocks 293 



I. INTRODUCTION. ACKNOWLEDGMENTS 



In 1899, Mr. E. D. Self, a graduate of the School of Mines 

 -of Columbia University sent a small suite of peculiar eruptive 

 rocks, which occur near the mines at San Jose, Tamaulipas, 

 Mexico, to Professor Kemp. They were at once recognized as 

 tinguaite and nephelite syenite, of great scientific interest. A 

 second shipment from Mr. Self of a larger series showed the 

 presence of camptonite and andesite. In December, 1901, the 

 writer accompanied Professor Kemp to San Jose with the ob- 

 ject of studying the copper ores and the neighboring eruptive 

 rocks. It was arranged that the writer should take up the 

 petrographic investigation of the latter, and the results are here 

 submitted. He cannot sufficiently acknowledge his indebted- 

 ness to Professor Kemp, not only for the opportunity so gener- 

 ously given him of studying the rocks petrographically, but 

 also for encouragement of every kind during his work. Every 

 facility was afforded him by Mr. Self, to whom his grateful 

 acknowledgments are due, as also to Mr. W. H. Nichols, Jr., 

 president of the San Carlos Copper Company. Dr. H. S. 

 Washington very kindly analyzed specimens of the nephelite 

 syenite, and of the tinguaite. The writer is anxious to express 

 his obligations to him for this, and for invaluable assistance 

 in the analytical work and calculations. The work was carried 

 on in the geological laboratory of Columbia University. 



