362 ME. A. M. EINLAYSON ON THE NEPHEITE [A.Ug. I909, 



on polished faces in the same direction its hardness is 5 to 5-5, 

 amounting at times to 6. 



Under the microscope (PL XYI, fig. 1) it is seen to consist of 

 a colourless aggregate of dense serpentine-fibres, of almost ultra- 

 microscopic fineness, arranged in wavy or corrugated laminae 

 and showing aggregate polarization. The laminae, when examined 

 under a high power, are seen to be much plicated and sheared, 

 forming a felted mass. This microscopic structure evidently ex- 

 plains the great hardness and toughness of the mineral, exactly as 

 in the case of nephrite. The mineral is optically negative, like 

 antigorites or laminated serpentines ; but it does not show the 

 structure of antigorite derived from augite, as has been described by 

 Prof. Bonney in the case of the Afghanistan bowenite [21, p. 169]. 



It contains small included aggregates of magnesite and patches 

 of infiltrated ferric oxide, these two constituents being the cause of 

 the striking sheen and colour-effects seen in prepared specimens. 

 Small grains of chromite are also frequently present, and Ulrich 

 has recorded bowenite from the Cascade Paver containing grains of 

 awaruite [13, p. 629]. The whole structure, as seen under the 

 microscope, gives emphatic proof of intense dynamic effects in the 

 formation of the mineral. A few residual flakes of talc occur, in 

 places, scattered through the mass of the mineral. The following 

 analyses indicate its composition : — 



I [18]. II [25]. Ill [25]. IV [25]. 



Si0 2 



. 44-77 



40-20 



41-20 





4591 



FeO 



3-35 



12-10 



12-10 





1-67 



MgO 



. 3917 



33-20 



34-02 





35-07 



H 2 



. 12-94 



12-70 

 98-20 



12-94 



A1 2 3 .. 



12-67 







Totals .. 



. 100-23 



100-2fi 



. 5-63 



1 0095 



Nos. II, III, & IV contain traces of MnO and Or 2 3 . 

 Specific gravity = 2*61. 



The Anita Bay mineral is very similar, petrographically and 

 chemically, to the original bowenite from Smithfield, Rhode Island 

 [26], and to that from Afghanistan described bv the late General 

 McMahon [27]. 



Bowenite matrix. — This rock, which contains the bowenite- 

 veins, has a greyish-green colour in the hand-specimen, with a 

 scaly structure and soapy feel, and a hardness which varies from 

 1-5 to 4. 



Under the microscope, it is seen to consist of coarse plates of talc, 

 generally much shattered and crushed, surrounded and veined 

 with magnesite and finely-laminated serpentine clearly derivative 

 from it (PI. XVI, fig. 2). The talc has a foliated structure, and 



