150 KEMP'S ORE DEPOSITS. 



them, doubtless formed, as at Eureka, Kev. (Example 36), by 

 surface waters and having no genetic connection with the ore. 

 Evidences of hydrothermal action along the contact are abundant. 

 The Copper Queen and the Arizona Prince are the principal mines. 

 There are minor deposits in the porphyry of oxidized ores above, 

 changing to chalcocite and this to chalcopyrite in depth. 1 



2.04.22. Example 20c. Globe District. As in the other dis- 

 tricts, the most productive mines are in limestone near the contact 

 with eruptive rocks. 



1. Contact deposits in limestone. At the Globe mines the 

 Carboniferous limestone abuts against a great dike of diorite, 

 while trachyte and granite are near. Along the contact there is 

 abundant evidence of thermal action in the kaolinized rock. The 

 great bodies of oxidized ores are found on this contact and extend 

 out into the limestone. The one on the Globe claim is described 

 by Wendt as resembling a great chimney. 



2. A fissure vein in sandstone, containing arsenical and anti- 

 monial copper ores and known as the Old Dominion, was formerly 

 worked. 



3. Fissure veins in talcose slate and gneiss, and filled by a 

 quartz gangue with bunches of malachite and azurite (New York 

 and Chicago mines), and now no longer worked. 



4. Numerous small veinlets forming a stockwork, in gneiss 

 near a dike of diorite, which is crossed by a dike of trachyte. 

 These are known as the Black Copper Group. The ores are too 

 low grade for profitable exploitation. Of greater interest are the 

 bodies of chrysocolla, found in the wash, down the hill from the 

 outcrop of the veins, and evidently due to the superficial drainage 

 of the stockworks. Similar bodies of ore, though not chrysocolla, 

 were found at Rio Tinto, in Spain. 2 



2.04.23. Example 2Qd. Santa Rita District. Although in Xew 



1 J. Douglass, "Copper Resources of the United States," M. E., Sep- 

 tember, 1890. Rec. A. Wendt, " Copper Ores of the Southwest," M. E., 

 XV., p. 52. Rec. 



2 J. Douglass, "Copper Resources of the United States," M. E., Sep- 

 tember, 1890. Rec. "The Globe District,?' Engineering and Mining 

 Journal, April 9, 1881, p. 343. W. E. Newberry, "Notes on the Produc- 

 tion of Copper in Arizona," School of Mines Quarterly, VI. 370. A. Trip- 

 pel, " Occurrence of Gold and Silver in Oxidized Copper Ores in Arizona," 

 Engineering and Mining Journal, June 16, 1883, p. 435. A. Wendt, " Cop- 

 per Ores of the Southwest," M. E., XV., p. 60. 



