A RELATION BETWEEN THE GEOLOGY AND 

 .METALLURGY OF GOLD. 



By F. T. MuMFORD, A.LM.M. 



(Abstract.) 



The author classifies the best-known gold mines in Rhodesia 

 under three main heads, namely: (i) Deposits in which gold may 

 have been laid down wnth the strata owing to decomposition of a 

 gold-bearing rock; (2) reefs and masses of igneous origin where 

 the gold has crystallised out with the matrix; and (3) sedi- 

 mentary schistose deposits. The first of these three groups he 

 subdivides into (a) recent alluvial deposits, and (b) con- 

 glomerates. Group 2 is subdivided into (a) true fissure, 

 imbedded and gash veins, and (&) masses of igneous origin. 

 He then points out incidentally that diflferent treatment is re- 

 quired for schistose and for igneous deposits. He goes on to 

 bay that alluvial deposits (group la) are generally treated by 

 catching the coarse grains of gold in ripples and amalgamating 

 the fines, and that coniglomerates (group ib) may also be 

 amenable to direct amalgamation and cyanidization after reduc- 

 tion to a sufficiently fine state to allow of the fullest application 

 of those processes. The Witwatersrand, Shamva and Eldorado 

 occurrences are mentioned in illustration. Reefs and masses of 

 igneous origin, provided no base metal, such as copper, antimony, 

 or arsenic is associated therewith, would also be free milling. 

 Of the schistose deposits the author mentions the " Enterprise " 

 find " Cam and Motor "" as examples. He explains the refrac- 

 tory nature of these deposits by assuming the metal to be either 

 in a state of chemical combination or present as brown 

 amorphous gold, and therefore gold in this condition needs for 

 its extraction specially designed plants. The " French Bobs " 

 and " Mount Morgan " occurrences are quoted as instances 

 hereof, and under the most favourable conditions, it is stated, 

 samples from these mines will not show more than a 50 per cent, 

 extraction with ordinary treatment. The geological formation 

 with which the gold is associated has. therefore, in the author's 

 opinion, a distinct bearing on the metallurgy of the ore. 



ELECTRIC CLOCKS. 



By Prof. Heixrtch Bohle, M.I.E.E. 

 [Not printed.) 



