19G W. II. WEED MINERAL VEIN'S ENRICHED BY SULPHIDES 



Sterry Hunt wrote:* 



" The curious phenomenon of t lie occurrence of the black ores in these deposits 

 between the gossan above and the unchanged pyri tons ores beneath has often been 

 described, and there seems no reason to question the received explanation that 

 they owe their origin to the reduction, in some imperfectly explained way, of the 

 sulphates formerly generated by oxidation in the upper portion of the lodes, which, 

 as is well known, is changed into a porous mass of hydrous peroxide of iron hold- 

 ing more or less oxide and green carbonate of copper in its lower portions. 

 Pyrrhotine is not without action on copper solutions, and its agency has been, with 

 great probability, suggested by Professor Henry Wurtz as accounting for the pre- 

 cipitation of copper sulphide." 



Secondary ores are described as consisting chiefly of sulphides, some- 

 times with an excess of iron, but more commonl} 7 with a large percent- 

 age of copper oxide. They are said to approach copper glance in compo- 

 sition, and it is said that crystals of glance have been observed by Mr 

 August Raht in this ore, which at times approaches bornite and chal- 

 copyrite in composition, and held in it grains of copper or crystals of red 

 oxide. 



"It is commonly impregnated with copper sulphate, the drainage waters from 

 which contain large quantities of this salt. As high as 5,000 pounds a month of 

 cement copper have been obtained from these waters, in which the percentage of 

 copper is about .001." 



Henrich, in a paper on the Ducktown ore deposits,f says: 



" The black copper found below the gossan had a very little black copper ore or 

 tenorite (CuO) in its composition. Most of the copper in it probably occurs as 

 copper glance, giving to it the black color. Native copper and cuprite are occa- 

 sionally present; malachite and silicates were found usually near the edges of the 

 black copper ore bodies, and in seams and stringers in the lower part of the gossan. 

 The walls alongside of the black copper zone were penetrated by seams and fissures 

 extending 5 to 12 feet from the ore body and carrying green carbonates." 



The following analysis made by Doctor A. Trippel is quoted by sev- 

 eral authors in their descriptions of the Ducktown deposits : 



CuO 5.76 3.80 



Fe 2 O s 1.50 .63 



S 18.75 25.40 



Cu 71.91 41.01 



* Fe 93 26.56 



Sol. sulph 72 1.78 



99.56 99.17 



♦Trans. Am. Inst. Mining Engineers, vol. ii, 1S74, p. 127. 

 f Ibid., March, 1895, p. 37. 



