THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XXXIY. — Mineralogical Notes ; by C. H. Warren. 



I. Native Arsenic fronv Arizona. 



A RECENT discovery of native arsenic at Washington Camp, 

 Santa Cruz Co., Arizona, adds still another interesting occur- 

 rence of this mineral in North America to those ah-eady 

 recorded. 



We are indebted to Mr. George A. Lonsbery, superintendent 

 of the Double Standard Copper Mine, now operated by the 

 Copper Century Mining Co. of Boston, Mass., for calling the 

 attention of Professor W. O. Crosby of the Massachusetts Insti- 

 tute of Technology to the occurrence, and for generously pre- 

 senting him with the best and largest part of the find. The 

 specimens, together with the following data regarding its occur- 

 rence, were very kindly placed with the writer for study by 

 Professor Crosby. 



The arsenic occurred in reniform masses attached to the 

 walls of a small pocket in a dolomitic limestone. The pocket 

 was situated in close proximity to an important fault at a depth 

 of about sixty feet. Many of the masses are remarkably fine 

 ones, weighing in some instances several pounds, while the 

 aggregate weight of the arsenic was something over fifty 

 pounds. The limestone of the region is highly metamorphic 

 and is traversed by two parallel and closely adjoining veins of 

 copper ore (chalcopyrite, sphalerite and some galena with a 

 gangue of garnet, quartz and calcite) on which some develop- 

 ment has been done. The faulted zone is characterized by 

 considerable brecciation. Masses of igneous rock, granite and 

 an acid porphyry outcrop in the immediate neighborhood, and 

 their intrusion is undoubtedly closely connected with the for- 

 mation of the ore-bodies, and also with the subsequent faulting. 



Am. Jour. Sci.— Fourth Series, Yol. XVI, No. 95. — November, 1903. 

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