﻿300 Huntington — Crystalline Structure of Iron Meteorites. 



most striking resemblance to the Widmanstattian figures. Such 

 examples as these indicate clearly that the Widmanstattian fig- 

 ures are not a peculiar phenomenon, but that such an alterna- 

 tion of plates is often a characteristic of crystalline structure, 

 when the process of crystallization is attended by the elimina- 

 tion of foreign material. 



There is another feature of the Widmanstattian figures 

 which often appears, and which is best explained by the as- 

 sumption that the process of crystallization was extremely 

 slow. Figure 10 shows two faces of a very perfect octahedron, 

 drawn of original size, from the Cranberry Plains (Poplar 

 Camp) iron. It will be seen by this sketch that the octahedral 

 outline has been sharply formed ; but while many of the Wid- 

 10. manstattian plates are parallel to this 



outline, there are others which are 

 markedly curved. These curved 

 plates must have originally formed 

 through the liquid mass as true planes, 

 like their neighbors, and have been 

 bent in the subsequent solidifying of 

 the remaining material. For. if they 

 Cranberry Plains. had been distorted by an exterior 



force, the regularity of the octahedron would have been at the 

 same time destroyed. 



This phenomenon of curved plates has been made a basis of 

 subdivision in the classification of iron meteorites. But it is 

 evident from the figure that the bending is not a constant or 

 essential character, as the plates are not all curved, but only 

 appear so at particular parts of the mass, and some specimens 

 show no trace of such a feature. In a word, such curved plates 

 are simply accidents of the crystallization. Yery similar bend- 

 ing is common in various minerals, as in gypsum, and very 

 conspicuously in the beautiful crystals of stibnite which within 

 the few last years have been brought from Japan. 



A similar remark might be made in regard to the swellings 

 formed in the kamacite plates around inclusions of troilite, 

 schreibersite, and the like, which have been so minutely de- 

 scribed by Eeichenbach, and named by him " Wiilsteisen."* 

 These again are accidents of crystallization, which have their 

 counterpart in other crystals, and are most beautifully shown 

 on the plates of mica from Chandler's Hollow, Delaware, 

 where the depositions of magnetic oxide of iron on the planes 

 of the crystalline growth of the mica produce effects which 

 imitate in a most striking manner the Widmanstattian figures. 

 We give in fig. 11 as perfect a representation of one of these 

 mica plates as could be obtained by the photographic process 



* Poggendorff's Annalen, 1861, cxiv, 477. 



