54 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Brezina 5 classed the meteorite as an octahedrite with fine lamellae in the Hraschina 

 group. He gives the breadth of the bands as 0.5 mm. and notes that the plessite is bright. 

 Meunier 6 grouped the meteorite as Caillite, and described its structure as follows: 



The figure given by the iron of Bear Creek is finer than that of the iron of Caille, and in some characters it departs 

 a little from the type without being altogether distinguishable. The kamacite, in little bands alternating with the 

 lamellae of taenite, forms compact groups, at times thick, which surround places occupied, now by plessite associated 

 with taenite, and now by pyrrhotine enveloped by an extremely thin layer of graphite. Schreibersite occurs in 

 scales at times quite abundant. 



Leick 7 noted a parting in the troilite of Bear Creek, which indicated that it crystallized 

 in the isometric system. The planes which he recognized by goniometric measurement 

 were those of the cube and dodecahedron. Later, however, he 10 concluded that these 

 measurements were not trustworthy. He found 8 the troilite of the meteorite a good con- 

 ductor of electricity. 



Preston 8 gave the following note regarding the locality of the meteorite: 



Bear Creek has been noted in most catalogues as having been found in Denver County, Colorado, which is a mistake, 

 as Colorado has no county by this name. It was first mentioned by Shepard as found upon the eastern slope of the 

 Sierre Madre Range of the Rocky Mountains. Again Henry notes it as found in a deep gulch near Bear Creek, about 

 25 or 30 miles from Denver. Smith in describing this meteorite gave it the name of Bear Creek. As Denver is on 

 the boundary line between Arapahoe and Jefferson Counties, and as there is a Bear Creek extending clear across Jefferson 

 County from west to east, emptying into the Platte, according to Henry's description, this would bring the locality 

 of the Bear Creek meteorite in the western central part of Jefferson County. Therefore, it seems likely that the iron 

 noted in the Shepard collection as "Jefferson, 30 miles from Denver," is in reality a portion of the Bear Creek meteorite 

 labelled "Jefferson" meaning Jefferson County, and that the date of fall, June, 1867, is an error. Particularly so as 

 the Bear Creek is described by Henry as being "shattered at one end," so that email pieces could be readily detached. 



Denver County has evidently been substituted for Denver city in many of the meteorite lists, as no county is 

 given in any of the early reports of the Bear Creek meteorite. Moreover, the Sierre Madre Range is west of Denver, 

 and Bear Creek is described as having been found on its eastern slope, which, in all probability, would bring it in Jeffer- 

 son County. So it would seem best that "Jefferson " should be discarded entirely as a distinct fall and be called Bear 

 Creek, and that Denver County in all meteorite lists should read Denver city. 



Cohen " described the structure of the meteorite as follows: 



The lamellae are long, straight, swollen, seldom grouped, and consist of strongly hatched granular kamacite, with 

 very fine etching pits and well-developed taenite. Since the hatching lines penetrate without hindrance the forks 

 between the granules, the latter are separation phenomena and do not indicate a granular structure of the kamacite. 

 The fields are uniformly distributed and vary little in their size. They are strongly developed, although somewhat 

 subordinate to the bands. The gray, rather bright plessite consists, as a rule, of grains whose size averages 0.03 mm., 

 and varies between boundaries of 0.02 and 0.10 mm. On strong magnification grains appear in it surrounded by delicate 

 taenite-like borders and separated by fine veins distinguished by lack of luster and by a dark color from the nickel-iron 

 of the grains. Since it is remarkably depressed it is perhaps a nickel-free or nickel-poor iron. At the edge of the 

 fields the grains go over into short, compressed bands. Plessite of this character was described by Tschermak from 

 Ilimae. Taenite ramifies into many fields and the kamacite grains often lie isolated in the taenite groundmass whick 

 is sharply distinguished by its smooth surface, luster, and light yellow color, and seems to be an outgrowth of the taenite 

 surrounding the bands. Again, in other fields, the dull, depressed black veins extend, producing a very fine-grained 

 or striated structure, and form a groundmass in which are imbedded isolated kamacite grains. Finally, some fields 

 show combs which, in consequence of their unusual breadth, are plainly outgrowths of the bands. Rarely does the 

 intimate structure of plessite exhibit itself so clearly. Schreibersite is very richly present. In part it forms large 

 crystals up to 15 mm. in length, occasionally showing hieroglyphic forms; in part there are smaller individuals which 

 either lie in the bands, producing a lumpy shape, or are surrounded by typical swathing kamacite. At times one can 

 plainly see that the latter is a deformed lamella, since one such lamella of normal development widens at the end 

 to a ring which incloses a grain of schreibersite. In addition, small shining grains and short rods occur in many bands 

 which likewise appear to be schreibersite but could also be cohenite. Large troilite nodules surrounded by swathing 

 kamacite show a peculiar angular-granular appearance and a lamellar structure of each grain gives a resemblance to the 

 so-called coral ore. 



The meteorite is chiefly preserved (436 pounds) in the Amherst collection. 



BIBLIOGRAPHY. 



1. 1866: Shepard. Amer. Journ. Sci., 2d ser., vol. 42, pp. 250-251. 



2. 1866: Henry. Mass of meteoric iron in Colorado Territory. Idem, pp. 2S6-287. 



3. 1867: Smith. Amer. Journ. Sci., 2d ser., vol. 43, pp. 66-67. 



4. 1867: Jackson: Analysis of a meteoric iron from Colorado. Idem, pp. 280-281. 



5. 1885: Brezina. Wiener Sammlung, p. 210. 



