364 Transactions. — Geology. 



mentioned the Waitai, Otaraa, Maori Dream, and Black Jack 

 Mines. 



Immediately overlying the clay-shales come a series of 

 diabase-ash and breccia beds. These are principally developed 

 in the high, conspicuous, abruptly-ending ridge which lies 

 between the two main branches of the Kuaotunu Eiver. This 

 ridge extends from the "Junction " at the Red Mercury battery 

 to the sources of the river. 



As seen in the low-level drives of the Red Mercury and 

 Great Mercury Mines, these rocks consist of a series of 

 greenish-grey diabase-ash and breccia beds, interstratified 

 with smaller beds of a dark-grey slaty shale and slaty breccia. 

 The ash and breccia beds decompose most readily into red 

 and brown clays, and in the shallower parts of the mines their 

 true nature cannot be determined. In the solid they are in- 

 tensely hard and tough, and their presence has added greatly 

 to the cost of the development of the reefs in the Red and Great 

 Mercury Mines at the low levels. They are traversed by the 

 Try Fluke, Red Mercury, and other parallel reefs, which follow 

 their course and underlie. 



These diabasic rocks are not found on any other part of the 

 peninsula, and their presence here as gold-bearing strata may 

 indicate a greater persistence of the reefs than has been the 

 case in the other goldfields of the Hauraki district. The 

 well-known Try Fluke reef, enclosed in these rocks, has been 

 traced through the leases of the Kapai, Try Fluke, Carbine, 

 Red Mercury, Great Mercury, and Irene. It possesses well- 

 defined walls, and varies in width from 2ft. to 20ft. Its 

 average width is probably about 6ft. Its course is N.N.E.- 

 S.S.W., and its dip easterly at angles seldom under 60°, and 

 more often over 65°. It has been proved to continue down- 

 wards in the deepest workings so far undertaken upon it. 



The nature of the quartz varies in different parts of the 

 lode. In some places it is hard, cavernous, and stained black 

 and browui with manganese-oxides ; in others it is mullocky, 

 friable, and crumbling, and stained rusty-brown with iron-per- 

 oxide. At the outcrop, near the Red Mercury low-level drive, 

 the lode-matter possesses a pure white colour, and occurs in 

 peculiar tabular bundles made up of thin layers or laminae of 

 friable quartz, which look like pseudomorphs after some of the 

 heavy earths. 



The gold is alloyed with about 35 per cent, of silver, and 

 it exists principally in an extremely finely-divided state. The 

 patches of rich quartz which are so characteristic of the reefs 

 at the Thames and Coromandel are not known in this reef or 

 in any other reef in this district. 



