31.— DRY CRUSHING OF ORE PREPARATORY TO THE 

 EXTRACTION OF GOLD. 



By Franklin White. 



The extraction of gold from the rock or from the other minerals 

 in which it is contained may at first sight seem to be a matter of 

 commercial rather than scientific nature. A judicious application of 

 scientific knowledge is, however, generally found to be of great 

 assistance to industrial enterprises. 



The Gold and Diamond industries are of great importance to 

 South Africa as a whole, as it is, comparatively speaking, a young 

 country as regards its advance in agriculture and in manufacture of its 

 raw materials ; the application of science as affecting gold extraction 

 especially as regards South Africa may, therefore, be reasonably in- 

 cluded in the discussion of this Society. 



It is impossible to say when or in what manner man first collected 

 and made use of gold. Recent research in Egypt has shewn the 

 existence there of very ancient circular crushing mills very similar to 

 the South American and Mexican " Arrastra " (a word indicating 

 '• dragging," from the verb " Arrastrar," to drag, referring to the 

 dragging of mullers or stones over the ore to be crushed), or to the 

 pug mill of the modern builder. 



It is claimed that both in papyri and in sculptures, in the ruins 

 of Beni Hassan and Thebes, the system of gold extraction then in 

 vogue is shewn, the general features being the breaking up and pound- 

 ing of the quartz containing gold until the fragments were made 

 small enough to set free the precious metal, which was then washed 

 out on sloping tables. 



The modern stamp mill, which is nothing but a collection of 

 pestles and mortars moved by mechanical means, is a f>erfected sur- 

 vival of this system. Quicksilver has, however, been made use of as 

 a means of collecting the gold more completely and expeditiously. 



The modem " blanket strakes " is nothing more than a cheap, 

 though efficient, substitute for the sheep skin, amid the hairs of 

 which the gold was formerly collected, and the Grecian fable of 

 Jason and the Golden Fleece is probably a poetical reference to a 

 successful raid on a community of alluvial gold washers. 



Certain negroes are reported to collect gold by pouring water 

 and sand containing gold on to the woolly heads of their fellows, and 

 then picking out the precious metal. 



Man would probably first find gold in alluvial deposits, its pre- 

 sence there resulting from the breaking up and wearing away of gold- 

 bearing rocks by atmospheric disintegration, earthquakes, avalanches, 

 and .subsequent pounding in the mountain torrents. 



He would then discover gold in the parent rock, and pound it 

 free himself. 



