NOTES ON SOME PSEUDOMORPHS, PETRIFACTIONS 

 AND ALTERATIONS. 



By AUSTIN F. ROGERS, 



Stanford University, Cal. 



(Read February 4, 1910.) 



The writer wishes to place on record some interesting cases 

 of pseudomorphs, petrifactions and alterations observed by him 

 in the last few years. Some of these are recorded for the first 

 time, some are American occurrences of minerals known abroad, 

 while others are good examples of commonly occurring pseudo- 

 morphs. While many examples of such pseudomorphs and altera- 

 tions are of mineralogical interest only, some of them have a possi- 

 ble bearing on the origin of ores. My thanks are due to the 

 gentlemen named in the several items who have kindly furnished 

 me with the specimens which make this paper possible. 



Pseudomorphs. 



1. Copper after Cuprite. — Calumet-Arizona Mine, Bisbee, Ari- 

 zona. Collected by Mr. E. W. Rice. Cubes of 4 mm. diameter, 

 modified by faces of the octahedron and dodecahedron occur in 

 cavities of a limonite gangue. The copper consists of dense aggre- 

 gates of small imperfect crystals with smooth cube surfaces. No 

 cuprite was observed in the specimen. 



2. Copper after Chalcanthite ( ?) — Carlisle, Arizona. Collected 

 by Mr. Harry Robertson. The specimen is a coarsely fibrous seam 

 of native copper 2 cm. wide. There are no associated minerals to 

 give a clue as to its origin and the mode of occurrence is unknown, 

 but as copper is practically always a secondary mineral, and as the 

 structure is exactly similar to well-known seams of chalcanthite 

 from Arizona, it is believed to be a pseudomorph after chalcan- 

 thite. 



PROG. AMER. PHIL. SOC, XLIX. I94 B, PRINTED JUNE II, I9IO. 



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