AUSTRALIAN MINING-FIELDS 131 



forming the rich alluvial deposits; 1 and only the roots of the 

 gold shoots remain. 



(c) Broken Hill 



The success of the saddle-reef mining at Bendigo has led 

 miners elsewhere, to watch eagerly for the occurrence of 

 these delightful simple conditions ; and saddle reefs have been 

 reported which have proved to be arched reefs of different 

 origin. It is not uncommon for a quartz reef formed along a 

 bedding plane to give off a branch across the bedding, along 

 a big joint or a fault plane. In such cases the main reef will 

 usually continue above the junction of the two branches, and 

 thus a transverse section shows three rays instead of two. It will 

 be shaped like an inverted Y instead of a saddle (fig. 4). Even 

 if such an arched reef has only two limbs, they are different in 

 origin, the bedding being parallel to one limb and transverse 

 to the other. Such reefs are therefore known as " false saddle 

 reefs." It is all-important to distinguish between true and false 

 saddle reefs, because there is no certainty that false saddle reefs 

 will recur in depth. 



A second type of false saddle reefs occurs in contorted 

 metamorphic plutonic rocks. The most important Australian 

 type of these reefs is at the silver, lead, and zinc mines of 

 Broken Hill. Broken Hill is a low ridge, about 2 miles long, 

 of foliated rocks, and forms part of the Barrier Ranges in 

 the western plains of New South Wales. It lies 70 miles 

 north-west of the Darling River at Menindie, and 30 miles 

 from the South Australian border. The hill was crossed by 

 Sturt in his famous inland journey in 1844, but no one suspected 

 its mineral wealth until 1883. It was then part of the Mount 

 Gipps sheep-run ; and some of the station hands, their attention 

 having been turned to mining by the discovery of silver in 

 the Thackeringa Ranges, 20 miles to the west, began to work 

 the manganese gossan of Broken Hill as a tin-mine. They 

 failed to get any tin, but found silver, and mining was begun by 

 the Broken Hill Proprietary Silver Mining Company in 1885. 



The rocks of the field have been described as altered Silurian 



1 Saddle reefs of a similar type to those of Bendigo occur in Nova Scotia, and 

 the interesting reports of Faribault show that the reef distribution is in some 

 respects like that of Bendigo and Castlemaine ; but the distribution of the gold in 

 this field is still imperfectly known. 



