Dry Crushing of Ore. 363 



As his knowledge expanded, fire would be used as an efficient 

 aid, eventually bringing him to smelt such rocks or minerals as were 

 suitable. 



Although these methods in process of time were vastly improved, 

 no notable advance in a new direction was made until Messrs. 

 MacArthur and Forrests made a commercially successful application 

 of the already known possibility of dissolving gold by means of cyanide 

 solutions, and the subsequent collection of the precious metal by 

 using zinc to effect its precipitation. 



At first sight this system appears to be simplicity itself. All 

 •that is required is (in theory) to break up the rock containing the 

 gold into sufficiently small particles, put the whole into a bath of 

 cyanide solutions, and then collect the gold as before explained. 



Metallurgists have always recognised that the recovery of .gold 

 by stamps only was limited to say 65% of the actual contents of the 

 ore, and that there was always a more or less considerable proportion 

 lost w^hich remained in the sands and muddy waters produced by 

 ■their stamp mills. 



They eagerly availed themselves of the new method for collect- 

 ing what was before an apparentlv unavoidable loss. 



The following figures will give an idea of the advantage obtained 

 by this successful application of a scientific fact : — 



Gold Outjjut on the Rand in first eight months of 1899: — 



Ore milled 6,067,317 ions. 



Gold produced (fine) 2,976,766 ounces. 



Value ^[2.468,617 



This gold was obtained: — 



Ounces. 



From Mills 1,945,236 equals 65.35% 



From Concentrates, etc. 74)294 ,, 2.50% 



By Cyanide 957.236 „ 32.15% 



2,976.766 .. 100.00% 



VALUE. 



Mill Gold ^8,161,185 



Concentrates 304,398 



Cyanide 4,003,034 



Total value ;^i2,468,6i7 



It can be correctly said that the additional amount of gold won 

 by the use of cyanide converted gold mining on the Rand from a 

 probably insignificant average profit-giving industr}- into a very re- 

 munerative undertaking. 



This new and important process has. however, not been 

 accorded its proper place. Instead of being considered as the final 

 and principal operation up to which the others should lead, it has 

 .been tacked on as an auxilian- to stamp mills and amalgamation 



