NICKEL-IRON ALLOY AWAKUITE OF NEW ZEALAND. 627 



the few specimens they collected, it may fairly be concluded that per- 

 haps all along that boundary there occur certain gabbro-rocks, either 

 as irregular intrusions and dykes, or as formed by gradual transition 

 from the peridotite through accession of plagioclastic felspar, disap- 

 pearance of the olivine, and exchange of the light coloured enstatite 

 for the dark ferriferous bronzite, and may be hypersthene and 

 diallage. Which of these suppositions is the correct one is doubtful. 

 Both kinds of relations between peridotites and gabbros have been 

 described by Professors Judd * and Bonney f from Scotland and 

 Cornwall respectively, and are also known from several European 

 districts. From the travellers' descriptions the intrusive mode of 

 occurrence of the gabbro seems the more probable. At uncertain 

 distances away from the peridotite-boundary, within the schist- 

 rocks, they found dykes of augite-porphyry and felspar-porphyry, 

 and bosses of a peculiar rock consisting of a white felspathic base 

 with long, thin, prismatic crystals of a fine green colour, reminding 

 us of epidote or actinolite. Of this unfortunately they lost the 

 sample X- 



We now come to the peridotite of the Olivine Range. Of this 

 there are only a few specimens available, and these present two va- 

 rieties very different in microscopic aspect, and also easily distinguish- 

 able from any of the Red-Hill rock. The variety said to be most 

 abundant on the range has a greenish ash-grey colour, looks very 

 close and dense, and consists of olivine and enstatite, the former 

 much predominating. Its special texture is, doubtless, owing to the 

 advanced degree of serpentinization it has undergone, though micro- 

 scopic examination of a number of thin sections, cut at various 

 angles from a specimen, seems to indicate that the enstatite has, in 

 the aggregate, suffered by this process quite as much as, if not more 

 than, the olivine ; this is an occurrence rather at variance with what 

 is usually observed and with the stronger tendency of the latter 

 mineral to decompose by atmospheric action, as shown by its 

 removal from between the grains of enstatite on the surface of 

 these rocks. Every grain of enstatite is more or less attacked along 

 cracks of cleavage and cross-cracks. Some appear broken up, as it 

 were, into a multitude of longer and shorter columnar pieces of 

 varying width, occupying collectively much less space than the 

 serpentine between them (see PL XXIY. fig. 7). A small pro- 

 portion are wholly converted into this mineral, which, in most cases, 



"^ Quart. Journ. Geol, Soc. vol. xli. 1885, p. 583. 



t Ibid. vol. xxxiii. 1877, p. 904, and vol. xxxiv. 1878, pp. 778, 779. 



I Among the specimens sent from the Red Hill are examples of varieties 

 of serpentine allied to picrolite, marmolite, and antigorite, vrith the common 

 dark-green type of the mineral, the latter sometimes containmg specks of 

 Avs^aruite as well as of pyrite and magnetite. In small nests and veins of the 

 serpentine of the Red Hill the following minerals were found : — Garnets (both 

 of light-brown and light-green colour), quartz, a chlorite (probably ripidolite), 

 asbestos or mountain-leather (probably chrysotile), magnetite, and massive talc 

 (steatite or soapstone). From massive outcrops in the same district rock- 

 specimens were collected, which are referred to bronzite-gabbro, common gabbro, 

 augite-porphyry or melaphyre, and labradorite-porphyry. 



