found at Makariwa, near Invercargill, New Zealand. 57 



kind of chondrule under notice is shown in fig. 1 (only one example 

 was found in the several sections). In this the mass of the chondrnle 

 is constituted partly of fine granular dusky olivine, partly of an 

 assemblage of large clear grains of this mineral, and has a ring of 

 small clear grains of the same surrounding the fine granular part, 

 whilst there is a border of dark grains of iron minerals around the 

 whole. In another kind of chondrule the mass is divided or fractured 

 by strong dark cracks into rudely parallel, columnar, and much cross- 

 fractured portions, which generally extinguish between crossed nicols 

 parallel to their length. The divisional cracks are sometimes so close 

 together as to impart to the whole a coarsely fibrous structure. Some 

 large chondrules occur also, exhibiting several systems of parallel 

 cracks which meet at various, generally obtuse, angles, and in others, 

 again, the cracks are eccentrically radiating. All the sections show 

 patches of roundish or quite irregular outlines, which have a striking 

 porphyritic structure, arising from the prevalence of an extremely fine 

 granular dusty base, through which are distributed comparatively 

 large clear crystals and irregular grains of olivine, and also occa- 

 sionally enstatite ; the base is probably also composed of a mixture of 

 granules of these two minerals. Serpentinisation of the olivine was 

 not observable in any of the sections. 



Enstatite. — Besides appearing in the porphyritic mode just men- 

 tioned, this mineral occurs also sparingly distributed amongst the 

 larger olivine grains and more abundantly in well defined chondrules. 

 In the first case, it forms either columnar bodies, sometimes broad, 

 but mostly narrow, or irregularly outlined grains — in fact, its forms 

 are very similar to those of the olivine ; and, as its colour is also next to 

 identical with that of the latter — if anything, that of enstatite being 

 fainter — the two minerals can hardly be distinguished in common 

 transmitted light. In polarised light, between crossed nicols and on 

 rotation of the stage, the difference is, however, very marked in that 

 the colours of the enstatite are of a low order— only various shades 

 of yellow and grey — contrasting strongly with the brilliant red, blue, 

 and green colours of the surrounding olivine. One has to guard, 

 however, against mistakes in this respect, as olivine grains cut at, or 

 nearly at, right angles to one of the optic axes — of which there are 

 examples in every section — show similar colours on rotation of the 

 stage. The employment of convergent polarised light solves this 

 question at once, and, in most cases, strongly marked cleavage-cracks 

 are seen in enstatite, parallel to which extinction takes place, whilst 

 generally, also, a finely fibrous structure becomes apparent on slightly 

 lowering the polariser with its top lens. The chondrules are of rather 

 dusty aspect throughout, or in cases only around the circumference, 

 and have mostly an eccentric or fan -like fibrous structure, as shown 

 respectively in fig. 2, lower margin, and fig. 5, upper margin, On 



