358 MK. A. M. FINLAYSON ON THE NEPHRITE [Aug. 1909,. 



structure and occasionally the typical thorn-structure of antigorite. 

 There is no evidence of derivation of the antigorite from pyroxene,, 

 and this variety appears here to he due chiefly to pressure and 

 movement along shear-zones in the serpentine mass. 



Pyroxenite. — This rock, when fresh, consists of cleavage-slabs 

 of colourless or pale yellow diallage (often very coarse). Brown 

 patches of schillerized inclusions are frequent, and the formation 

 of bastite is often noticeable. 



Serpentine-pyroxenite. — This type is an altered peridotite,. 

 containing serpentinized olivine and colourless diallage. The 

 diallage occasionally shows marked uralitization, the crystals having 

 a broad selvage of fibrous amphibole with an extinction-angle 

 of 16° to 19°. Some bastite in the rock may represent original 

 enstatite. 



Gabbro. — This rock, which occurs only in small veins, consists 

 of saussurite and uralite. The original plagioclase, of which a few 

 hazy outlines may sometimes be seen, has been almost completely 

 altered into a fine-grained aggregate of saussurite. The hornblende 

 is a pale green variety, occurs plentifully in rectangular or irregular 

 plates, and occasionally encloses cores of original pyroxene. At 

 other times the octagonal cross-section of augite has been preserved, 

 in the hornblende. 



Petrography of the Contact-Zone. 



Garnet-pyroxene rock (PI. XV, fig. 3). — This type, the- 

 syenite of Davis [7, p. 115] and the saussurite-gabbro of Hutton 

 [14, p. 146 J, has been shown by Prof. Marshall to be a rock com- 

 posed of diallage and grossularite-garnet [17, p. 321]. As the 

 last-named writer has pointed out, it is highly probable that 

 both the garnet and the wollastonite mentioned above represent 

 portions of limestone that have been caught up and digested by 

 the peridotites in their ascent. 



Epidote-rock (PL XV, fig. 4). — This variety, which passes, 

 gradually into epidote-serpentine rock, occurs as included lenticles. 

 in the serpentine in association with the copper-ores along the 

 limestone margin. It is grey to straw-yellow in colour, and contains, 

 veinlets and grains of chalcopyrite. In section it shows a mass of 

 epidote in needles and columnar crystals, thickly interlaced. These- 

 are set in a ground-mass of fibrous serpentine and of finer epidote- 

 needles, which latter are only resolvable under a high power. The 

 epidote is pale yellow or colourless, and the following analysis of 

 carefully selected material shows it to be a lime-variety : — 



