The Meteoric Irons from Griqualand East, South Africa. 13 



A. — The Iron from " Kokstad" in the Vienna Collection. 



For examination I have had at my disposal two sHces weighing 

 163 and 54 grams, with cut surfaces of 51 and 18 sq. cm. respec- 

 tively, the larger being the property of the Hofmuseum, Vienna, and 

 the smaller of Greifswald University. 



Especially characteristic is the occurrence of the kamacite in two 

 different types. One portion of this mineral occurs mainly in 

 straight-lined beams, which, frequently joined closely together, 

 and arranged parallel to the octahedral faces, attain a length of 

 2-5 cm. ; less frequently it occurs in small round-ended lamellse 

 which seem to be irregularly arranged. This form, when etched, 

 assumes an uneven surface and gives in consequence a dull orientated 

 shimmer. Seen through a hand lens the surface shows a fine- 

 grained structure, but, viewed by higher powers, it is seen that the 

 unevenness is due to numerous fine etching-hollows and etching-lines. 

 The latter are usually gently undulating and sometimes so arranged 

 in parallel lines as to give the beams a striped appearance. 



The other less abundant type of kamacite occurs in short 

 lamellse with highly rounded ends which are never closely joined 

 together. The lamellse are generally 1-2 mm., exceptionally 1 cm., 

 long ; they assume an evenly etched surface with a very strong 

 orientated sheen and show few somewhat indistinct Neumann 

 lines (" schwach schrafiirter Kamazit"). The larger lamellas lie 

 parallel to the octahedral faces, the shorter are as irregularly arranged 

 as the shorter lamellae of the first type of kamacite, and, with these, 

 form apparently irregular groups which cover nearly half of the 

 surface of the slice. Not infrequently all kinds of kamacite — 

 especially the short, stubby types — are intimately intergrown to form 

 what is seemingly 07ie lamella composed of dull, and of glittering 

 grains. Owing to the marked differences in the strength of their 

 lustre, the various beams stand out sharply from one another, 

 and from this, as well as from their varying size and arrangement, 

 produce on the etched surface a peculiar broken appearance such as 

 I know on no other octahedral iron (see Plate V., Fig. 1). Taenite 

 is very poorly developed. The fields are small but numerous, and 

 consist of remarkably dark, finely granular plessite, in the centre 

 of which sti-ongly lustrous flakes are often massed together ; 

 "combs" are always quite isolated. 



The Greifswald slice, which comes directly from the surface of the 

 block and is covered on one side by a portion of the oxidized crust, 

 differs from the Vienna piece just described, in having the strongly 



