126 The Philippine Journal of Science wis 



the calcite content, the results would be the same, I have not 

 considered copper reactions in this discussion. 



The principal characteristics of this class of deposits due ap- 

 parently to the presence of the calcite are : 1, The mine waters 

 are neutral or alkaline at practically all horizons above ground- 

 water level ; 2, owing to this fact no free chlorine can be formed ; 

 3, should nascent chlorine be formed, it would readily attack 

 the moist calcite, so that little or no chlorine would remain un- 

 combined and free to attack the gold ; 4, should gold chloride be 

 formed, some of the gold at least would be precipitated at ap- 

 proximately the same horizon by ferrous sulphate produced by 

 the oxidation of the iron pyrites. 



In the Philippine calcite-bearing ore deposits the manganese 

 seems to be associated with the calcite in the primary ore. 3 All 

 the evidence available confirms this conclusion. Therefore, 

 wherever manganese is found, either calcite or calcium carbon- 

 ate in solution is present and would neutralize any acids, 

 or has been present and has already neutralized the acids. If 

 any acids are formed, it is evident that where they are formed 

 there is no calcite or calcium carbonate in solution and conse- 

 quently no manganese. Under such conditions, ferrous sulphate 

 would be formed, and it would appear that if there is insufficient 

 calcium carbonate to neutralize the acid there would also be 

 insufficient manganese oxide to oxidize the ferrous sulphate. 

 This condition would leave active an agent which precipitates 

 gold. 



ANALYSES OF MINE WATERS 



In the analyses of mine waters * it is noted that acid hydrogen 

 was determined or found to be present in only 10 out of 29 cases. 

 The facts that in the general average of mine waters 295 parts 

 per million are calcium and 77 parts per million are the carbonic- 

 acid radicle might account for some of the 19 cases where acid 

 hydrogen was not reported and in which the mine waters were 

 neutral. 



Analyses were made of mine waters of the calcite-gold deposits 

 of the Philippines to determine, primarily, free chlorine and 

 acidity. 



s Fanning, Min. Resources P. I. for 1911, Bur. Sci., Div. Min. (1912), 44. 

 4 Emmons, opus, cit., 773. 



