vm, a, 2 Edding field: Calcite-quartz-manganese Gold 129 



hours. No free chlorine was found in the solution, and no gold 

 was dissolved. 



Experiment No. 3. — A sample of the ore mixture was placed 

 in a bottle, with 0.5 gram of finely divided gold and freshly made 

 chlorine water, and agitated for eight hours. The resulting solu- 

 tion gave a strong test for free chlorine, but contained only a 

 trace of gold. 



Experiment No. 4- — Two parallel chlorination tests were run. 

 No. 1 was made up of finely ground calcium carbonate, 0.5 gram 

 of finely divided gold, and freshly made chlorine water. No. 2 

 was made up of finely ground quartz, 0.5 gram of finely divided 

 gold, and freshly made chlorine solution. These were agitated 

 for one hour. No. 1 solution gave a strong test for chlorine and 

 calcium, and showed a trace of gold. The calcium was dissolved 

 to form CaOCl 2 and possibly CaCl 2 . No. 2 gave a strong test 

 for chlorine, and showed a large percentage of gold dissolved. 



In the case of No. 1 the chlorine attacked the calcium carbon- 

 ate first, but the great excess of chlorine gave it an opportunity 

 to dissolve some gold as well. Another test, in which the chlorine 

 was in contact with the gold and calcite for forty-eight hours, 

 showed that a very large percentage of the gold had been dis- 

 solved. The reaction of chlorine with calcite would be more 

 important in an ore deposit where there is relatively so small an 

 amount of chlorine. 



Experiment No. 5. — Calcium carbonate was added to gold- 

 chloride solution, boiled for five minutes, and filtered. No gold 

 was precipitated. 6 The filtrate was almost colorless. It con- 

 tained a large amount of calcium, probably as a complex salt of 

 calcium and gold. 



These experiments demonstrate that no acid could be formed 

 in veins containing calcite, except in waterways in the parts of 

 the vein where calcium carbonate is not encountered. It is prob- 

 able that even in such cases the acid would travel but a short 

 distance before coming in contact with, and being neutralized 

 by, calcite or calcium carbonate in solution. Chlorine cannot be 

 liberated except in the presence of acid, and consequently no 

 free chlorine or very small amounts only would be formed in 

 the type of vein under discussion. 



If the gold were ever dissolved as gold chloride, it could be 

 precipitated by ferrous sulphate, metallic sulphides, calcite, 

 organic material, or bacilli at or near the same horizon. 



8 W. H. Emmons recently has found that gold is precipitated from cold 

 dilute solutions by calcite. I have not yet seen this in a publication. 



116737 i 



