10 Annals of the South African Museum. 



the tuff-like appearance so characteristic often of chondritic meteor- 

 ites, is here wanting. On the other hand, there is also an absence of 

 the fused granular aspect of the ground mass which Tschermak lays 

 stress upon for the so-called " granular chondritic meteorites," 

 and on account of which he characterised them as fritted 

 stones. 



The crust, about ^ ^o i nii^- thick, shows up very well by reflected 

 light, especially when viewed by a lens, but in transmitted light, 

 under the microscope, the outlines, owing to the incomplete fusion 

 of the constituents, are not w^ell defined. Not only are fragments of 

 silicates, still doubly refracting, plentiful, but quite unaltered nickel 

 iron may be detected by its lustre. At all events, one can see 

 under the microscope that the crust does not, as so often happens, 

 form a homogeneous substance. A 002 to 005 mm. wide outer 

 zone contains only sparse and very small silicate fragments, and 

 brownish transparent isotropic patches which may consist of glass. 

 Next there comes a zone about twice as wide which is rich in 

 silicates, usually in fragments, but also in larger pieces, and apparently 

 no alteration has taken place here. The third zone, which merges into 

 the kernel, is much poorer in silicates and shows a fair quantity of 

 nickel-iron blebs. Glass has not been found here, but it does not 

 follow that it is wanting, the sections not being very thin. The 

 outer zone is undoubtedly the actual crust ; the other two may well 

 be compared with Tschermak's segregation ■■'■ and impregnation 

 zones, though the distinguishing features are not neai'ly so sharply 

 defined as is the case with chondritic meteorites of more spongy 

 structure. In the photograph (Plate III., Fig. 3) these zones are 

 not clearly differentiated, the slides being so little transparent ; 

 still they are indicated on the middle portion defined by two 

 cracks. 



Of the silicates, enstatite is by far the most common both in the 

 matrix and in the chondrules. In the former it occurs as a rule as 

 stout, irregular prisms, with longitudinal partings, an actual fibrous 

 structure being rare and then not distinct ; in the sections at right 

 angles to the vertical axis the pyroxene cleavage is prismatic and 

 very perfect.! Apart from opaque ores, no inclusions have been 

 observed. On the part of the enstatite chondrules a confused 

 radiated structure is most characteristic, Plate III., Fig. 2, showing 

 a good example. Here the fibres are, as a rule, of about the same 

 size, and only occasionally is there a stouter crystal, giving rise thus 



* Vide E. Cohen, Meteontenkunde, Heft ii., 113-115. Stuttgart, 1903. 

 t The slides are at right angles to the first + bisectrix. — C. K, 



