METEORITES OF NORTH AMERICA. 433 



An account in detail of the component minerals is also given by Smith. His analysis of 

 the meteorite as a whole is given under I, of the troilite under II, and of the schreibersite 

 under III. 



Total Sp. gr. 

 99. 22 7. 89 ' 

 99. 01 4. 75 

 99.69 7.017 



Harris 4 was persuaded that the lawrencite was first formed after the fall. Reichenbach ' 

 called attention to the regularity of the Widmannstatten figures and the delicacy of the taenite 

 threads; he also mentioned an "Ablosung" and a fragment of magnetic pyrites over an inch 

 in size bordered with yellowish iron sulphide. 



Rammelsberg 5 raised the question whether iron sulphide in iron meteorites was pure iron 

 sulphide or magnetic pyrites, considering the results of Smith not decisive, although he him- 

 self, as it seems did not doubt that the former was present. Rose ' observed thin strips of 

 schreibersite, which followed only one system of straight bands and considered that Tazewell 

 is distinguished thereby above all other meteoric iron. Wright * investigated the gases. 



Meunier * 15 concluded at first, from the analysis by Smith, that Tazewell consisted only of 

 tsenite, later he stated that plessite was also present in considerable quantity. The mark desig- 

 nated by Smith to differentiate troilite from magnetic pyrites he regarded as insufficient. He 

 noted the ready cleavage of the iron sulphide and the presence of graphite, bordered with schrei- 

 bersite. When he stated that Smith had observed a regular crystal of iron chloride, he must 

 have been mistaken. 



Sorby " cited Tazewell as a distinguished example of fine and especially beautiful Wid- 

 mannstatten figures; he considered it free or almost free from schreibersite and composed of 

 two alloys qf nickel iron, one of which was readily attacked by weak acid, the other, when first 

 crystallized out, was not at all affected thereby. He compared the structure with the kind of 

 ice which consists of a skeletonlike network and meshes filled out later. According to him, 

 Tazewell belongs to irons with original structure in contrast with those formed by later crys- 

 tallization (for example, Ruffs Mountain). 



In 1880 Brezina u called attention to the relationship of Tazewell with Butler in structure, 

 occasioned by the strong predominance of plessite and taenite, and left it doubtful whether the 

 extremely thin core of the lamellae is to be regarded as identical with the kamacite. He men- 

 tioned troilite and schreibersite plates as minor ingredients. In 1885 he M separated Tazewell, 

 together with a few other irons as finest octahedrites from those with fine lamellae, and char- 

 acterized the same as a fine network of extremely fine lamellae not grouped; tsenite about the 

 same in quantity as the plessite or the latter predominating to some extent; kamacite scarce, 

 as in the case of Butler; bands from .05 to .1 mm. broad. 



Cohen 23 described the meteorite as follows: 



Tazewell is poor in kamacite, not in consequence of the small number of bands, but because of their narrow width; 

 nevertheless, by strong magnifying it is distinctly marked off from the surrounding well-developed tenite bands, 

 which are prominent in the lamellae. The fields predominate in a considerable degree and show varied formation. 

 One portion consists of dense and very dark plessite ; it is only by strong magnifying that one can discern a structure 

 of fine granules with occasional inclusions of tiny glistening pointe; this plessite is very readily affected by acid and 

 appears to be identical with the kamacite of the bands. Another portion of the fields appears bright by reason of 

 strong reflection of the light, is hard to affect by acids, and is composed of an intimate mingling of dense kamacite 

 and numerous small, uniformly distributed leaves of tsenite. In many places both sorts of plessite are represented by 

 very nearly equal areas of considerable extent; in other places one sort predominates, and thereby arises a characteristic 

 change in the appearance of the etched surfaces. Occasionally there occur in the areas of the twofold sort comblike 

 excrescences, which vary from the width of the principal lamellae to microscopic fineness, and only very rarely fill 

 entirely or nearly so a small field. 



Dodecahedral lamellae of nickel iron were described by Brezina and Cohen, 16 which origi- 

 nating from the octahedral structure, usually reached halfway into the fields and inclosed a 

 center of schreibersite. According to Brezina's 22 more recent investigations it is the lamella 1 

 716 15 28 



