131 



are so predominant in this class as to render the ore unfit for amal- 

 gamation, while the percentage of silver in the Stromeyerite is too 

 great to allow of its being treated profitably in the barrels. This 

 class represents about ten per cent, of the entire amount of ore, 

 and the average of its yield of silver, calculated on the entire 

 amount smelted, is nearly $1,000 to the ton of 2,000 pounds, while 

 the amount contained is about fifteen per cent. more. 



The second class contains the same minerals as the first, but they 

 are more intimately associated with the gangue, which in this class 

 forms the bulk of the ore. The blende and galena have a moderate 

 percentage of silver, (thirty to fifty ounces) while the tetrahedrite 

  (Fahlerz, or Gray Copper ore) varies from one to one and a half 

 per cent., and the Stromeyerite is said to rise as high as twenty- 

 six per cent. Chlorobromide of silver and native copper have 

 occurred, and native silver in small flakes is frequent. Two varieties 

 of quartz are found, one in the ordinary glassy form, often comby ; 

 and an opaque white variety, very brittle and associated with the 

 richer minerals. 



Crystalhzed specimens are very rare, and of the copper-silver- 

 glance none have been observed. 



I have observed the following well defined paragenetic successions 

 occurring in cavities : 



quartz ; 2 brownspar ; 3 scalenohedral calcite. 

 brownspar ; 2 barytes ; 3 scalenohedral calcite. 

 quartz ; 2 galena ; 1 quartz, 

 quartz; 2 blende ; 3 calcite. 



quartz ; 2 blende ; 3 rhombohedral calcite ; 4 native sil- 

 ver ; 5 scalenohedral calcite. 



/. 1 quartz ; 2 brownspar ; 3 barytes ; 4 native silver. 



From this it will appear that the general succession in age is : 

 1st. quartz; 2d. brownspar; 3d. blende, barytes; 4th. calcite; oth. 

 native silver; 6th. scalenohedral calcite. From this list the rela- 

 tive ages of blende and barytes do not appear. 



Galena, blende and tetrahedrite are usually closely associated 

 with each other in this ore, while the argentiferous sulphuret of cop- 

 per is entirely independent of them, but is, at times, mixed with 

 erubescite. 



Native silver occurs in the common filigree form in cavities in 

 the argentif. copper-glance, and is often observable in minute specks 

 on the tarnished surface of blende and tetrahedrite. 



The reduction works are on the Arivaca ranch, eidit miles dis- 

 tant from the mme, and connected with it by an excellent road. 

 The process used is the European barrel-amalgamation for argen- 

 tiferous copper ores, and was introduced by Mr. Kiistel, a German 

 Metallurgist, about three years since. The extent of the works is 



