268 PROCEEDINGS OF SECTION C. 



and that "it is universally admitted throughout the field that a 

 moderately hard tufaceous sandstone country is the class of rock 

 most favourable for gold, and that where this is pyritous and 

 carries small black veins — (of protosulphide of iron (?) ) — which 

 run into the reefs, rich deposits ahiiost always occur."* Sir James 

 Hector also says "all varieties of these rocks are auriferous only 

 in proportion to the amount of sulphides they contain."! 



From this we may infer that the most favourable country is 

 where the rocks have gone through the first and second stages of 

 decomposition already descz'ibed, having been changed into what 

 the miners call " kindly sandstone," and especially where these 

 rocks are abundantly charged with pyrites. However we must 

 remember that numerous auriferous veins occur in the hard rocks 

 also, and that the greater expense of working them here may 

 account for some of them having been failures. Also, 1 much 

 doubt if Sir James Hector's induction is founded on a sufficiently 

 wide basis of fact ; but I shall have to return to this subject 

 again. 



Facts connected ivith the lodes. — Gold occurs in the veins in four 

 ways — (a) in auriferous pyrites, (b) scattered in small grains through 

 massive quartz, (c) in threads or scales, some of which are pseu- 

 domorphs after botryogen or copiapite, ;j; between the points or 

 quartz ciystals in comby veins, the quartz at the base of the 

 crystals being often stained red, and (d) in calcite at the Success 

 Mine, Coromandel. It is never found enclosed in a quartz crystal. 

 Mr. W. Skey§ says that he " was not able to observe any other 

 matrix than quartz, or highly quartzose rock, where the gold at 

 least was in paying quantity." 



In some of the claims in the upper and middle portions of 

 Taruru Creek manganese oxides occur along witU the gold to the 

 almost entire exclusion of iron compounds. || The auriferous veins 

 usually contain abundance of pyrites, but other sulphides — 

 stibnite, blende, arsenical-pyrites, copper-pyrites — are in small 

 quantity only, and these have been introduced subsequently to 

 the golcl.H Carbonates of lime and of iron have been introduced 

 into the veins after the quartz.** 



According to Mr. Davis, the occurrenjce of " pyrites in the 

 matrix of the lodes is a sine q^ua non" that "the hanging wall of 

 roof need not of necessity carry pyrites, but rather the richness 

 of the reef is increased by the diminution of pyrites in the roof, 

 provided that the foot wall is rich in them," and that " leaders 



* Reports Geological Explorations, 1882, pp. 23 to 44. 

 T Reports Geological Explorations, 1868-9, p. 27. 

 J Campbell, Trans. N.Z. Inst. XIV. p. 457. 

 § Reports Geological Explorations, 1870-1, p. 84. 

 il Reports Geological Explorations, 1S70-1, p. 85. 

 i Reports Geological Explorations, 186^-9, p. 24, and ibid 1882, p. 44. 

 ** Reports Geological Explorations. 1867, p. 8, and ihid 1868-9, p. t'. 



