AUSTRALIAN MINING-FIELDS 135 



5. The Indicators of Ballarat 



That Australia was one of the great goldfields of the world 

 was first proved in 185 1 by the discovery of the gold-bearing 

 gravels of Golden Point, at Ballarat East. The quartz veins 

 from which these gravels gained their gold are of interest in 

 mining theory, owing to the indicators, which have secured for 

 Ballarat mention in most recent books on ore deposits. 



The early miners of Ballarat were faced by the paradox of 

 finding gold in large nuggets and coarse grains in the gravels, 

 and yet the adjacent hills, though the rocks were exceptionally 

 well shown, contained no quartz veins comparable in size to 

 the nuggets shed from them. Hence arose the belief that the 

 nuggets grew by slow accretion in the gravels from percolating 

 gold solutions. This theory has been now almost universally 

 abandoned ; but it is of historic interest as indicating the 

 difficulty of believing, that the nuggets could have been derived 

 from the small, irregular quartz veins, that seam the hills of 

 Ballarat East. 



The nuggets found in the surface gravels and soils of 

 Ballarat have been found along a line running north and south 

 through the town and suburbs of Ballarat East. The nuggets 

 were no doubt formed in small quartz veins, where they are 

 cut across by narrow seams called indicators. These indicators 

 have been generally regarded as originally layers of sediment 

 especially rich in organic matter. Each indicator was thought 

 to have been deposited as one bed in the succession of clays 

 and sandstones laid down on the floor of a Lower Palaeozoic 

 sea. The decomposition of the organic matter was considered 

 to have formed iron pyrites in these particular bands of clay. 

 Later on the rocks have been tilted, until they are nearly or 

 quite vertical, and at the same time the clays have been cleaved 

 into slates and the sandstones altered to quartzites. Solutions 

 percolating through horizontal cracks in these rocks deposited 

 vein quartz ; and it was thought that the gold in the solutions 

 precipitated patches or nuggets opposite the seams of iron 

 pyrites. 



This theory has been so widely expressed in mining litera- 

 ture that it was a great surprise to me to find, on surveying 

 the Ballarat East mines for the Victorian Mines Department, 

 that it cannot be confirmed. The indicators are not inter- 



