PRIMARY SULPHIDE ORES. 89 



Gold. Gold is present in the average ore in the proportion of gold to silver 

 of 1:100 by weight. It has never been detected by the eye in the sulphide ores, 

 either in the hand specimen or under the microscope, though it has been found in 

 metallic particles both macroscopically and microscopically in the oxidized ores. 



ANALYSIS OP PRIMARY SULPHIDE ORES. 



Picked samples of rich primary sulphide ore were taken from the Montana 

 vein of the Montana Tonopah mine at depths ranging between -160 and 512 feet. 

 These were crushed and the sulphides were concentrated by panning. The analysis 

 of the concentrates by Dr. W. F. Hillebrand of the U. S. Geological Survey, is as 

 follows: 



Analysis of concentrates of primary sulphide ore from Montana Tonopah mine. 



Per cent. 

 Siliceous matter 15. 18 



Gold 82 



Silver 25.92 



Lead t 6.21 



Copper 1 . 32 



Iron 9. 87 



Manganese 1. 36 



Zinc 5. 84 



Selenium 2. 56 



Tellurium None. 



Arsenic 19 



Antimony 92 



Magnesia 1. 49 



Lime 3. 70 



Carbon dioxide 6. 34 



Sulphur Not det 



81. 72 

 The composition of the carbonate is as follows: 



Per cent (in terms 

 of u hole analysis). 



Lime carbonate (CaCO,) 6.71 



Magnesia carbonate (MgCO 3 ) 3. 13 



Iron carbonate ( FeCO 3 ) 2. 36=Fe =1. 14 



Manganese carbonate (MnCO s ) 2.57=Mn=1.32 



The whole of the manganese, therefore, exists as carbonate. 

 Doctor Hillebrand remarks: 



"Prolonged boiling with hydrochloric acid decomposed all the sulphide except 

 pyrite (and chalcopyrite if present). Hot dilute nitric acid then dissolved the pyrite 

 and also considerable selenide of silver (and copper?). The residue remaining after 

 this treatment consisted, aside from quartz, of very malleable black scales and parti- 



