﻿Vol. 64.] AND ANTIGORITE-SERPENTINES. 159 



Geological Survey, kindly sent me a copy of its ' Bulletin,' 

 which contained a description of some serpentines and other 

 rocks (designated the Pounamu formation), illustrated by un- 

 usually good and large figures of microscopic sections.^ Two of 

 these, entitled ' an altered olivine-rock ' and ' a serpentine-schist,' 

 obviously consist oi: antigorite, although that name is not used ; 

 indeed it would be impossible to have a finer or more characteristic 

 representation of the mineral than the former one aifords. Dr. Bell 

 states that these rocks must originally have been peridotites and 

 ' are generally massive, though sometimes fairly scliistose,' the latter 

 figure representing a variety from a region which has obviously 

 undergone great pressure-metamorphism. Our hopes of meeting 

 during his recent visit to England were unfortunately frustrated, but 

 1 received just before completing this paper a box containing about 

 a dozen fine specimens of dunite, serpentines, and allied rocks, 

 which in accordance with his instructions had been sent to me from 

 New Zealand. Four of these, the most important for my present 

 purpose, I had immediately sliced ; but 1 trust before long to 

 examine the remainder,-^ and tender my most hearty thanks to 

 Dr. Bell and other members of the Survey for so valuable a gift. 

 Of those four, the dunite (from the Dun Mountains, i^elson) is a 

 block, measuring nearly 7x5x3 inches, of greenish-yellow colour, 

 showing occasional blackish and dull-green specks, with a slight 

 cleavage, rudely parallel with the broader surfaces. Under the micro- 

 scope it is seen to consist chiefiy of grains of olivine, very clearly 

 exhibiting interrupted lines of crush, in which serpentinization 

 is incipient ; a few of the larger grains show a rather vaguely- 

 defined oscillatory twinning, probably also a result of pressure. A 

 little diopside is present in the slice, as also some rather rounded 

 subtranslucent and deep-brown grains of chromite, or perhaps in 

 some cases picotite. A handsome specimen of an ' actinolite-and- 

 talc rock from a boulder. Clear Creek, Mikonui (Toaroha District)/ 

 has a general resemblance to the rock described above (p. 156) 

 from the northern margin of the Geisspfad mass of serpentine ; but 

 the actinolites, many of which are rudely parallel, are more numerous 



^ New Zealand Geol. Surv. n. s. Bull. No. 1, * Greology of the Hokitika Sheet, 

 North Westland Quadrangle ' bj J. M. Bell & CoHn Fraser, 1906. See Oh. viii 

 (the plates are not numbered). The figures appear, with brief descriptions of 

 the slices (without, however, using the name antigorite), in Prof. Sollas's 

 Memoir on the Rocks of Cape Colville Peninsula, New Zealand, vol. ii (1906) 

 pp. 186-202. 



^ [Slices from these reached me immediately after this paper was read. The 

 following are most nearly connected with it: — (1) ' Ultrabasic rock. Dun 

 Saddle' : a dark comj^act rock, with some rather small bastite, consisting of 

 olivine, more or less serpentinized, bastite, sometimes much altered, (?) dial- 

 iage (one grain), and picotite. (2) ' Serpentine, Dun Saddle ' : a dark, i-ather 

 uniform serpentine, which shows under the microscope a pale yellowish-green 

 tint and the usual 'meshwork' serpentine, marked out by strings of magnetite- 

 granules, with a slight parallelism. There are some small grains of chromite 

 and a few (rather larger) of a more steatitic aspect, possibly indicating the 

 former presence of a pyroxene in very small quantities. Two other interesting; 

 specimens are described below.] 



Q. J. G. S. No. 254. m 



