﻿160 PROP. T. &. EONNEY ON ANTIGOEITE [May I908, 



and much larger, some being at least an inch long ; while the talc, as 

 becomes very plain on microscopic examination, is less abundant/ 



That the other two specimens were antigorite-serpentines was 

 obvious at a glance. One (boulder in Cross Kiver, Mikonui, Whit- 

 come Pass District), a somewhat flat flake, measuring fully 6x5 

 inches, and about an inch and a half thick, with a slight and rough 

 cleavage oblique to the broader face, is a mottled rock — dark 

 purplish-green, and lighter green, here and there irregularly streaked 

 with a still paler green. Microscopic examination shows it to be 

 composed of antigorite, with a fair amount of residual augite, perhaps 

 a few flakelets of talc, and iron-oxide, with a little sulphide. The 

 antigorite-flakes have a slightly tufted and occasionally somewhat 

 acicular habit, attaining not seldom a length of about '03 inch. 

 There is a fair amount of residual augite, often ' stabbed ' by the 

 other mineral, which, so far as I can ascertain, is not related to 

 the cleavage-planes of the augite, except that in a few cases, where 

 the remnant is a very narrow wedge, this extinguishes at a 

 rather small angle with its sides. The granules of iron-oxide are 

 irregularly distributed and in one or two places, which are free 

 from residual augite, they suggest the former presence of a ' mesh- 

 work.' Of the occasional larger grains, one is distinctly translucent, 

 and of a rich brown colour ; others slightly so : thus chromite, 

 or possibly picotite, must be present. The light-coloured streaks 

 mentioned above, when examined with a lens, included a mineral 

 with some resemblance to olivine ; but, as a little of the powder 

 showed under the microscope distinct, rather elongated, prisms with 

 a low extinction-angle, it must be a variety of actinolite. The 

 second specimen, from Griffin Range, Hokitika (Turiwate District), 

 is a still larger slab, rather darker in colour, which retains on one 

 side a portion of an external surface with a bright brown tint and 

 a slightly ' corded ' structure. A slice, cut perpendicular to, and in 

 the direction of, the slight cleavage, proves to be wholly composed 

 of antigorite and iron-oxide ; the latter being apparently not very 

 abundant or large in grain, but now and then pierced by the former, 

 to which it locally imparts a rich sienna-brown stain. The 

 antigorite-flakes are smaller, not more than one-third of the length 

 of those in the other specimens, and generally narrower in propor- 

 tion to their length. Some parts of the slice, where the smallness 

 is rather marked, show an approach to ' thorn-structure'; others a 

 distinctly tufted grouping, which occasionally is slightly cruciform 



^ A. specimen labelled ' coarse peridotite (Dun Saddle, IVelson), probablj- with 

 bronzite,' is crowded with close-cleaved specimens of the latter mineral, some- 

 times about an inch long or wide. Examination of ib, when powdered, leads 

 me to refer the bulk of it at any rate to diallage. [A slice, received since this 

 paper was read, shows that a diallage is the dominant mineral, but there is 

 some enstatite (probably bastite) ; and, I think, a few grains (sometimes 

 poecilitic) of a brownish-yellow, slightly-fibrous, obviously much-altered mineral, 

 probably representing a ferriferous member of this group (bronzite or perhaps 

 hypersthene). A grain or two of olivine may be present, with some granules 

 of iron-oxide. I should think it likely that the rock formed dykes or veins 

 cutting the dunite.] 



