82 Transactions. 



of their red colour, but the green rock is hardly to be distinguished from 

 the common darker green or black argillite. 



The material of the green argillites shows, under the microscope, quartz, 

 magnetite and pyrite, and sericite. The green colouring-matter is indeter- 

 minable ; in the case of green argillites examined elsewhere this colouring 

 has been considered to be epidote (9, p. 47) or amphibole (12, p. 99). 

 Haematite is the chief recognizable mineral of the red argillites. 



The so-called red and green slates are green argillites partly reddened. 

 Sometimes a gradual change of tint from deep red through light red to 

 green is observable. In other cases the colour changes abruptly from red 

 to green. Sometimes the red argillite shows veins of deeper red (Plate VI, 

 fig. 2). The appearance under the microscope with reflected light is of a 

 roughly equidimensional mass of grains, each coated with red, while in 

 places red colouring is gathered in veins which show a deeper tone. 



The description of the red clays and shales of Nova Scotia as given 

 by J. W. Dawson (19, p. 26) applies equally to the microscopic appearance 

 of these argillites : "" [the colouring-matter] having indeed the aspect of 

 a chemical precipitate rather ,than of a substance triturated mechanically. 

 In addition to oxide of iron distributed through the beds, there is, in fissures 

 traversing them, a considerable quantity of the same substance in the 

 state of brown haematite and red ochre, as if the colouring-matter had 

 been subperabundant and had been in part removed and accumulated 

 in these veins." 



Where the red argillites have been subjected to weathering, cleavage 

 is more pronounced ; and often the red colour has been leached out, leaving 

 a light-grey to white product. A similar result of weathering of argillite 

 has been noted by C. Fraser (18, p. 47). 



Writing in " The Geological History of New Zealand " (20, p. 164), 

 F. W. Hutton says, when speaking of the Maitai system, " In several 

 localities in both Islands red-jasperoid slates occur, sometimes associated 

 with manganese oxide, and this, together with the paucity of fossils and 

 the general absence of plant-remains, points perhaps to a deep-sea origin." 

 The manganese oxide which occurs in the rocks of the Wellington Pen- 

 insula is found in small nests or stringers in the softer strata. In most 

 cases it forms no more than an incrustation sufficient for blowpipe testing : 

 a sample from Duck Creek, Porirua, yielded 5-4 per cent, of MnOg. It is 

 never found as concentric shells around a nucleus, nor exhibiting mammil- 

 lated structure, nor yet impregnating a mass of palagonite or forming layers 

 alternate with any such substance — these being the more general modes of 

 occurrence of manganese oxide in deep-sea deposits (21 : 22). Here its 

 occurrence seems to have no more significance than that of iron oxides, and 

 in habit it appears to parallel closely the latter oxides. 



Further, the Maitai rocks of Wellington Peninsula, as mentioned be- 

 fore, yield plant-remains, these having been collected on both sides of the 

 argillites at Sinclair Head and elsewhere, while the black colouring-matter 

 of the argillites is presumably carbonaceous. Paucity of fossils is no 

 criterion of deep-sea deposits. The absence of radiolarian cherts and 

 glauconitic sands anywhere in the rocks of the Maitai series, as well as 

 the nearness in the series of conglomerate bands both above and below 

 the red and green slates, are evidence that the Maitai rocks are not of 

 deep-sea origin. 



Analyses Nos. 4 and 5 of the accompanying list are of green and red 

 argillite respectively. Save for the proportions of ferrous and ferric 



