220 



place cannot have originated later than the Devonian era at 

 least. 



As there are many speculations by able authorities regard- 

 ing the mode of origin of gold whether associated with quartz 

 or otherwise, I have specially added an appendix to this 

 paper, briefly dealing with the history of gold mining in 

 Australasia. In it will be found a reference to the specula- 

 tions of various authorities regarding its mode of origin. 

 The one most commonly accepted, viz., " hydrothermal 

 agency," is that which was favored by Dr. Barnard in a paper 

 read before this Society in the year 1880. This theory is 

 also favored by Dana, Lyell and. other authorities, and it 

 would appear also to be adopted by Mr. Thureau in respect 

 of such mineral formations as the "Iron Blow" at the Linda, 

 although the latter seems to be unaware of the fact that the 

 mode of origin of the more common auriferous quartz reefs 

 are also frequently ascribed to hydrothermal agency. 



GOLD. 



Gold is classed, with silver, platinum, iridium, and pal- 

 ladium, as one of the noble metals, and is widely distributed 

 throughout the world, principally in the rocks of Archaean 

 and Cambro- Silurian age. It occurs mostly in a native 

 state, being either pure or only slightly alloyed with 

 one or other of the following metals, viz., silver, tellurium, 

 copper, iron, bismuth, palladium, rhodium. Although gold 

 often richly occurs in the drifts, conglomerates, and igneous 

 rocks of more recent systems,— notably those of Tertiary age, 

 — it is now very generally acknowledged that the gold so 

 found has been derived primarily from the decomposition 

 and waste of the auriferous quartz reefs and veins which 

 occur chiefly in rocks of Silurian and Devonian age. It was 

 from the more recent auriferous superficial drifts, composed 

 of clay, sand, and gravel, that gold was first derived by man. 

 Beef gold mining, according to Davies, " although the oldest 

 mode of occurrence in nature, is the one more recently known 

 to men, and still more recently worked with success. Except- 

 ing some Brazilian mines, and one of doubtful success in the 

 Ural Mountains, there was, only forty years ago, scarcely a 

 gold mine profitably worked in the solid rock." 



Important Gold Discoveries in Modern Times. 



The following brief summary is confined to the more im- 

 portant discoveries of gold in the great producing centres of 

 modern times. For the facts relating to ex-Australian centres 

 I am indebted to Davies' useful work, " Metalliferous 

 Minerals and Mining," 8vo., pp. 438 ; London, 1851. 



