282 PROCEEDINGS OP SECTION C. 



Several of the beds described above in these two sections as 

 sandy shales and mudstones when further examined may prove to 

 be tuffs chiefly of volcanic origin. 



No microscopic sections have as yet been prepared of the 

 Heathcote cupriferous purple shales, but their external resemblance 

 to the Holt-Sutherland shales is so close as to make their tuffa- 

 ceous origin all but certain. 



At Holt-Sutherland out of a total thickness of seventy-one feet 

 at least three feet showed native copper more or less freely. 

 Seven and a-half inches of the core shewed native copper in 

 addition to those portions mentioned. 



At Heathcote about seven inches of core altogether were 

 cupriferous. 



MACROSCOPIC CHARACTER. 



Small hand specimens of the core from Holt-Sutherland shew 

 the rock to be of a dark purplish-black or greenish-purple colour. 



The texture varies from that of a grit containing particles one- 

 sixteenth to one-eighth of an inch in diameter to a very fine grained 

 compact shaley rock. The latter has a small conchoidal fracture, 

 while the former breaks with uneven wedge-shaped chips with 

 flatter surfaces. 



The fine grained rock, even when examined with a pocket lens, 

 shews no structure with the exception that here and there it is 

 seen to contain scales of native copper from one-twentieth to one 

 fourth inch in longest diameter, averaging one-tenth inch, and 

 about one-fortieth inch thick. 



Their prevailing shape is circular, more or less. 



The gritty tuff is seen withovit the help of the pocket lens to be 

 a fragmental rock composed of black, green, brown, red, and grey 

 particles. The average size is about one-twentieth of an inch, 

 though many of the fragments are from oiie-eighth to one-sixth 

 of an inch in diameter. On freshly broken surfaces of the tuft' 

 some of these particles shew bright cleavage planes. Minute 

 irx'egular grains and scales of metallic copper can easily be detected 

 in places, and rarely a thin plate of iiright native copper is seen 

 filling the interspace of a minute vertical joint. 



When soaked in water the fine and gritty tuffs gradually break 

 up into fragments of one-quarter to half an inch in diameter. 

 The fine tuff, however, even when soaked for several days, does not 

 become disintegrated or softened so as to form any fine sediment. 

 The gritty tuff, however, when similarly treated, yields a fair 

 amount of muddy material. 



The specific gravity of the gritty tuff is 2.62. The hardness of 

 the fine compact tuff" is from 2^ to 3. 



