818 



DIAMOND-DEPOSITS OF COPETON, X.S.W., 



and green. Well developed octahedral crystals are conspicuous; 

 probably 6 to 8 per cent, of the diamonds being of this nature. 



» A number of the crystals exhibit 

 twinning. Pieces of bort, several 

 carats in weight, have also been 

 found at this mine. 



The lead next passes through 

 Davis' block. Here it is also 

 concealed by basalt, though the 

 depth of the wash from the surface 

 is lessened by the fact, that a 

 small stream has removed a con- 

 siderable portion of the basalt- 

 capping. The lead, at this point, 

 swings round from a north-east 

 and takes a north-west course. 



At the Koh-i-noor Mine, which 

 is situated about 150 yards be- 

 yond the last-mentioned block, 

 the basalt has been removed from 

 the lead on its western side. A 

 section of the deposits (see Text- 

 fig 3) shows that the bedrock is a 

 very decomposed granite. Upon 

 this rests a body of gravel, some 

 three feet in thickness. There is 

 no prominent band of wash in 

 this, but the whole consists of 

 small quartz-grains and pebbles 

 about 4 mm. in diameter, which 

 have been derived from the de- 

 composition of the granite. Above 

 this lie three feet of pipeclay of 

 _ the same nature as that noticed 

 at Rider's lead. This, again, is covered by three feet of fine 

 granite-sand. The whole section has been exposed by tunnelling, 

 and is overlaid by basalt. Immediately to the west of this is 

 situated the redistributed, Tertiary gravels previously mentioned. 



