changed into pale green faintly pleochroic fibres with 

 straight extinction which again seems to be anthophyllite 

 though of a much less ferriferous type. With it is associated 

 a good deal of actinolite. The central portion of the olivine 

 pseudomorphs is either talc or finely interlocking quartz 

 grains. Occasionally the whole pseudomorph is made up 

 of interlacing amphibole fibres with irregularly scattered 

 quartz grains. The spinel is a remarkably greenish-brown 

 and is probably intenm-diuto in composition between pico- 

 tite and pleonaste. 



Talc rock. — Another mode of alteration of peridotite is to 

 a rock composed of pale green non-pleochroic, but highly 

 birefringent talc in areas separated by bands of dusty car- 

 bonate, evidently the survival of the intergranular cracks. 

 Each of these areas is made up of a complex of minutely 

 interlacing fibres and plates of talc showing mutual compen- 

 sation. Here and there the rock becomes a darker green- 

 brown and is fibrous and pleochroic. The extinction is 

 usually straight and the double refraction lower than that 

 of talc. This is perhaps chlorite. There are a few grain 8 

 of diopside-diallage and some picotite. This rock was once 



An interesting slide shows how greatly the 

 phosing condition varied in a small distance. A section of 

 dunite is in its central portion almost unaltered. Serpen- 

 tinisation is commencing in the usual way. One end has 

 passed completely into the green talc through an inter- 

 mediate band of darker pleochroic green. The other end 

 is in an advanced stage of serpentinisation, a little carbon- 

 ate and green silicate is present with it. 



Qmrtz-cu vbona I e-pieol ite rock.— A very noticeable rock 

 is found usually in the breccia. It is dull white or pale 

 grey in colour, and studded with black grains of spinel. Or 

 it may be grey with cloudy white or pale brown patches, 



