Vol. 65.] AND MAGNESIAN HOCKS OF NEW ZEALAND. 361 



altered to be of value for chemical analysis. As may be seen in the 

 descriptions of the rocks by Prof. Marshall [15], the characteristic 

 alteration-products are serpentine from olivine, saussurite from 

 plagioclase, and bastite and uralite from pyroxene. Prof. Van Hise 

 has pointed out that hornblende appears to be more stable than pyro- 

 xene under moderately deep-seated conditions of metamorphism [22], 

 and his conclusions are fully borne out by the modes of alteration 

 of the pyroxene-bearing rocks described in this paper. The uraliti- 

 zation of pyroxenes is a constant and characteristic phenomenon 

 in the New Zealand peridotites. 



(6) Other Occurrences in Western Otago. 



The serpentine-talc rock near Gibbston has been described by 

 Prof. Park [23] and by the present writer [21]. The serpentine- 

 rocks on the Caples River west of Lake Wakatipu, and in Windley 

 Creek south of the same lake, are of a similar nature. The 

 serpentine of the latter locality contains a good deal of pyrite 

 in places. 



(7) Milford Sound Area. 



At Anita Bay there occur dunite, hartzbergite, and a peculiar 

 talcose rock, all enclosed in highly-contorted gneissic granulite. 

 The talc-rock is the matrix of the interesting species bowenite. 

 The dunite and hartzbergite have been described by Prof. Marshall 

 [16, pp. 482-83]. It is worthy of note that the dunite shows a 

 pronounced cataclastic structure, and that the enstatite of the 

 hartzbergite reveals all stages of alteration into magnesite, the final 

 product being an olivine-magnesite rock which closely resembles a 

 marble in hand-specimens. Prof. Marshall has suggested that the 

 effect may be due to the solvent action of percolating waters charged 

 with organic salts derived from the dense vegetation which clothes 

 the hillsides [16, p. 483]. The olivine is in all cases perfectly fresh. 



Bowenite. — This mineral, the tangiwai of the Maoris, occurs 

 in irregular veins and seams ramifying through its matrix (to be 

 subsequently described, p. 362). The hand-specimen is generally of 

 a sea-green or olive-green colour, best seen when polished. It is, 

 when pure and free from flaws, highly translucent, and, owing to 

 its hardness, takes a very fine polish. Being softer than nephrite, it 

 is less suited for weapons or tools, and hence was little used by the 

 Maoris. Its translucency, however, is generally superior to that of 

 ' greenstone,' and reflections due to cloudy and scattered inclusions 

 impart to it often a very handsome appearance. It was, indeed, 

 the most beautiful of the stones known to the Maoris, and the one 

 least valued by them. 



The mineral is massive and scaly or fissile in structure, and its 

 hardness varies greatly according to the surface on which it is 

 tested. On fissility-planes it varies from 3 to 4 (Mohs's scale). On 

 surfaces cut at right angles to these planes it averages 4-5, while 



