The Meteoric Iron from Bethany, Great Namaqualand. 25 



divide into two portions, showing a considerable degree of structural 

 difference. One portion shows the normal structure of a finely 

 lamellar octahedral iron. The width of the lamellae rarely exceeds 

 0"33 mm. ; the beams are only now and then rounded at the ends, 

 and sometimes occur isolated, sometimes congregated together. The 

 kamacite is so finely hatched that the etching-lines and hollows and 

 the fine taenite borders are first distinctly seen on microscopic 

 examination, and it is only where a fourth lamella coincides with the 

 plane of section and has been preserved, that numerous and distinct 

 etching-lines become visible to the unaided eye. Granular structure 

 is wanting, or but slightly indicated. 



The well-developed fields which form quite half of this portion of 

 the surface are of very varying size and formation. The smaller 

 ones appear, as a rule, almost black, and even when viewed through 

 a hand-lens, uniformly dull, homogeneous, and compact. On 

 stronger magnification, however, numerous delicate, lustrous 

 spangles and a fine-grained structure become apparent. This 

 variety of plessite is most easily affected by etching. Its dimen- 

 sions rarely exceed a few millimetres, and it therefore plays but an 

 unimportant part in the composition of the iron ; still, its colour 

 being considerably darker than the rest of the nickel-iron, it shows 

 up very clearly. On Plate VIII. this is not the case, as some of the 

 beams there appear quite as dark as the plessite, but by aid of 

 a lens places showing the differentiation are easily discovered, 

 especially on Fig. 1. On the enlarged reproduction (Plate IX., Fig. 1) 

 the dark plessite stands out clearly at many places on the periphery, 

 where the mottled appearance also indicates the fine-grained structure. 



Of the larger fields, some are composed of irregular grains 0'03 

 to 0'2 mm. in size (Plate IX., Fig. 1), and on favourable etching, 

 groups of these show a strong, similarly orientated, sheen. The 

 sheen may be caused by etching-hollows, for stronger magnification 

 in reflected light reveals numerous minute lustrous specks. I think 

 I have also occasionally noticed a few etching-lines, but it is difficult 

 to feel certain of these, and I have similar uncertainty as to the 

 nature of an extremely fine taenite-like sheath. As a rule the grains 

 with their doubtful sheaths lie close together, but occasionally one 

 comes across dark, dull particles of from 0*02 to 0*05 mm. wedged 

 in between them, which closely resemble the first-mentioned plessite. 

 Similar fields were described and figured by Tschermak "^^ as being 

 in the iron from Ilimae (the same as Juncal according to Brezina). 



* Ein Meteoreisen aus der Wiiste Atacama. Denkschriften d. Mathem. Natur. 

 wiss. Olasse d. Wiener Akad d. Wissensch., 1871, xxxi. i. p. 193. Tf. IV., Fig. 6. 



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