METEORITES OF NORTH AMERICA. 59 



Brezina 6 definitely proved the association of tsenite with plessite in this mass. 



Meunier 7 describes it as a common type but possessing a very distinct character from the 

 association with nickel-iron of large quantities of troilite which is disseminated quite uniformly 

 throughout the rock, the same sulphide being also present as huge cylindrical forms enveloped 

 in a thick sheath of graphite and schreibersite. The result is a rock which does not conform 

 to any other.' 



Brezina 9 also describes it as a highly oriented iron with an almost complete fusion crust, 

 and one which can have lain in the open air only a short time prior to its discovery. On the 

 front side of the iron he notes — 



a fusion ridge resembling strands of hair parting asunder, while the rear side, 1 to 2 mm. thick, is covered with a gran- 

 ular crust which appears porous in cross section, and sometimes drops measuring 1.5 cm. in diameter are reduced to 

 0.5 cm. in thickness. The regular arrangement of laminae and interspaces, the very marked development of tsenite 

 and its extraordinary richness in schreibersite crystals make this iron one of the most beautiful and instructive 

 among known meteorites. The broad bordered kamacite bands are almost in equal proportion to the fields rilled with 

 shimmering plessite. On one part of the iron the triad is deformed, bent. The large schreibersite laminae, as much 

 as 5 cm. in length, are abundantly and evenly distributed throughout the entire mass; they are usually embedded in 

 kamacite 1 to 1.5 mm. thick and follow the octahedral laminae in their orientation. Numerous troilite concretions, 

 measuring 1.5 to 3.5 cm. are found intact on the inside and upon the rear side, but on the front side they are mostly 

 fused out ; in numerous places may be seen a tonguelike indentation of the troilite by the trias, which causes the envelop- 

 ing kamacite to follow the indentation like an intercalary layer. Occasionally, also grains of iron are found inside of the 

 troilite and a tongue of iron or included grains of iron may sometimes be observed inclosed entirely in graphite. It is 

 frequently found, that on the scaly borders of the trias, on the side toward the troilite granules, after the removal of 

 the latter, the laminae terminate in crystalline boundary surfaces. 



Schreibersite occurs in individual crystals, some of which resemble cohenite crystals; it also occurs in plates 1.5 

 mm. thick by 6 cm. in length and lying parallel to the octahedral facets; in fact, Bella Roca is distinguished by a very 

 unusual richness in schreibersite. The meteorite is also noted for the exceptionally high percentage of iron sulphide 

 it contains and for the large lumps in which it occurs. 



Cohen " described the structure of the meteorite as follows : 



Bella Roca is distinguished by long, straight, strongly swollen, few and weakly grouped lamellae, unusually well 

 developed taenite bounding uniformly distributed fields which are nearly equal in extent to the bands. The kama- 

 cite, which is occasionally somewhat coarse-granular, affords a uniform, dull, peculiar sheen. Under the microscope 

 it shows so fine a granulation that even under the strongest enlargement it can not be determined what produces it. 

 The fields consist almost wholly of opaque, dark plessite. As a rule they are uniformly penetrated by minute, shin- 

 ing scales. In the larger fields though, the shining inclusions are somewhat larger, and appear on strong magnification 

 as closed curves of various shapes 0.01 to 0.02 mm. in diameter surrounding dark grains. One such field is surrounded 

 by a broad, dark edge 0.05 to 0.1 mm. in width, not sharply bounded at the interior, which appears similar to the pre- 

 dominant plessite. Only a few fields cross the complete lamellae, which are about 0.05 mm. in breadth, and run out — 

 as a rule at both ends, though at times only at one end — into the principal lamella? so that their taenite border unites 

 with that of the latter. 



Bella Roca belongs to those irons which are distinguished by the number and size of the schreibersites, their 

 shape being partly elongate-prismatic, and partly elongate lenslike. On a plate having a surface of 300 sq. cm. 

 besides many smaller individuals, I counted 20 prismatic crystals 5 cm. in length. They are usually oriented par- 

 allel to the lamellae. Swathing kamacite is not distinguished from the rest of the kamacite. Two plates showed a 

 different magnetic relation. One which was nearly square took very strong magnetism; the other which was nearly 

 as long as broad, only weak magnetism. The former showed, according to the investigation of Leick, a specific mag- 

 netism of 1.C8, the latter of 2.39 absolute units per gram. Specific gravity=7.8244. 



Cohen " also reports an analysis by Knauer as follows : 



Fe 89. 68 



Ni 9. 78 



Co 0. 55 



Cu 0.02 



Cr Trace. 



P. 0. 31 



S 0. 05 



100. 39 



The meteorite is distributed, the largest mass being in the possession of the Vienna Museum. 



