22 



particularly near the moutli of the Eichmond Eiver, that profit- 

 able workings have been carried on, operations being, as a rule, 

 confined to patches of sand that have been naturally concentrated 

 by the sea. In addition to quartz — which can be readily 

 removed — the sands contain zircon in abundance, and some- 

 times tin-stone, both of which minerals are considerably denser 

 than quartz, and cannot be readily separated from gold by 

 washing. After concentrating the sand as much as possible, the 

 miner saves most of the gold by means of quicksilver, leaving the 

 platinum, tin-stone, zircon, and some of the gold in the 

 concentrates. The samples of sand exhibited are all concen- 

 trates, quartz having been removed by washing. It will be 

 noticed that the assay value of these concentrates varies much. 

 The character of the gold and platinum can be judged from 

 4069, the metals occurring as very minute flattened discs. It will 

 be readily understood hoAv difficult it would be to save this 

 material by mechanical processes such as washing. Quite recently, 

 however, successful concentration has been accomplished, 

 and parcels of clean tin-stone and platinoid metals have 

 respectively been placed on the . market. Specimens of these 

 concentrates are exhibited (10204). Inland there have been 

 found strips of loosely coherent sand coated by organic matter, 

 which are evidently of similar origin to those occurring on the 

 present sea-beach, but have been cut off by the erection of ridges 

 of sand-hills. These are known as " leads," and one of them — 

 McAulay's — yielded much gold (see 6317, &c.). The gold in 

 these leads is sometimes coated with substances which protects 

 it from the action of the quicksilver. Boiling with caustic soda 

 has generally overcome this difficulty. McAulay's lead has now 

 been abandoned. 



Alluvial. — In the Condobolin district — Fifield, Platina — 

 auriferous alluvial deposits yielding platinum have been worked 

 for some years. The platinum occurs as grains and nuggets. 

 The amount raised in 1899 was 638 oz., valued at £1,070. 

 Several nuggets are exhibited, one of which weighs 27 dwt., and 

 is the largest yet recorded from Australia. Platinum, like gold 



