97 



serpentine. There is also indications of the trace of the (001) 

 cleavage. In convergent polarized light good interference 

 figures were obtained. It was also noticed that the disper- 

 sion was p < V. The principal inclusions were grains of 

 magnetite and a few liquid and gaseous inclusions, with 

 little or no zonal arrangement. 



The mineral next in abundance is the rhombic pyroxene 

 enstatite, which is almost transparent, possessing a light- 

 brownish-green colour, slightly idiomorphic, and enclosed by 

 the olivine. The double refraction and refractive index are 

 noticeably less than olivine. Some of the sections are broken 

 into parallel plates along the well-developed cleavage, namely, 

 the (110). Some sections exhibit two fairly good cleavages 

 intersecting at 88°, and more rarely a fair cleavage at 45°. 

 A small amount of alteration has gone on, especially in the 

 vicinity of the cracks, the resulting alteration product being 

 a fibrous mineral, probably "bastite." The rare polysynthetic 

 twinning is very clearly seen between crossed nicols in the 

 larger sections. In convergent polarized light a biaxial in- 

 terference figure with a large optical axial angle is seen. The 

 optical sign is positive, and there is a slight dispersion, p < r, 

 which is an indication that the mineral is low in iron. The 

 principal inclusions are liquid or gaseous, sometimes zonally 

 arranged. Magnetite is present in a small degree. 



The diallage, which is light-green in colour, is slightly 

 pleochroic. There are two distinct cleavages intersecting at 

 89°, and sometimes traversed by a third. The extinction 

 angle, unlike the enstatite, which is straight, is oblique, being 

 identical with augite. In convergent polarized light, good 

 interference figures are obtained, the optical axial angle being 

 small, the two axes just skirting the edge of the field. The 

 optical sign is positive and p < v. The principal inclusion is 

 magnetite in the form of grains. Decomposition has gone on 

 to a noticeable extent, the products of decomposition being 

 serpentine and epidote. 



The brown isotropic mineral, picotite, is not infrequently 

 met with, being in the form of small rounded grains and irre- 

 gular masses. They are traversed by cracks and contain a few 

 inclusions. 



Order of Consolidation. 



Picotite ... ... ... 



Enstatite ... ... 



Olivine ... ... ... 



Diallage ... ... ... ... 



