27 



(From Talwal; on loan to the Museum.) 2654, from Berrima, Case 50. 

 is not unlike a fish, but liere Nature lias been assisted by Man, 

 the tail having been twisted. 



The Departmental collection of nuggets and many alluvial 

 specimens are not displayed, the intrinsic value being consider- 

 able. Of these the following may be mentioned : — ■ 



The "Maitland Bar" Nugget, found by Chinamen at Har- 

 graves in 1887; weight, 3-i4!-78 oz., containing 313-093 oz. of 

 fine gold, according to specific gravity test; value, £1,236 I4s. Id. 



A nugget of gold from Wood's Flat, near Cowra ; weight, 

 42 oz. 17 dwt. 5 gr. ; value, £168 5s. 5d. 



In case 137, immediately to the right of the entrance, is a 

 collection of casts of nuggets, some of which are from New 

 South "Wales. 



A few specimens of wash-dirt succeed the alluvial sold. Alluvial 



" wash-dirt,. 



A few explanatoi'y words, for the assistance of visitors unacquainted 



with mining terms, may be useful here. Rivers draining an area 



of gold-bearing country carry down rock debris into their valleys. 



In course of time this debris is ground down to gravel, sand, or 



mud, and may be carried for long distances. As the speed of the 



current slackens, on reaching more and more level country, the 



heavier portions of its burden will be deposited by the water, 



forming accumulations on the river-bed. With the rock-material 



there will be a certain quantity of gold, the particles of which,. 



being malleable, not brittle, are flattened or rounded by the 



pounding to which they have been subjected. Gold so deposited 



is known as alluvial gold, and the gravel, sand, or mud in which it 



is embedded is the "wash- dirt." When this wash-dirt becomes 



bound together into a coherent mass by cementing agents, such as 



oxide of iron, silica, &c., it is known as " cement " by the miners^ 



Gold-bearing wash-dirt is frequently found in the valleys of 



existmg rivers, and the gold may then be won by sluicing or 



dredging operations. It has sometimes happened, however, that 



a valley has been filled up by a flow of lava from one of the 



volcanoes that at one time existed in Australia, in which case the 



alluvial wash-dirt is buried under a cover of volcanic rock (mostly 



basalt), through which shafts have to be sunk to get at the 



alluvial below. Ancient river-valleys, filled up with gold-bearing 



alluA^ial deposits, and not now occupied by a running stream, are 



known as "leads," while those that are buried under a cover ot 



basalt or other material are " deep leads." 



