58 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XHI. 



infrequently occur with interiors made up of small rounded granules imbedded in a glaaa base, but extinguishing simul- 

 taneously with the outer portion. In many respects the microstructure closely simulates that of the San Emigdio 

 stone, but the apparent fragmental nature is less conspicuously marked. In two instances small irregular colorless 

 granules were observed giving faintly the twinning striae and inclined extinctions characteristic of plagioclase feldspars. 

 It is not possible from the examination of the two slides at command to state more definitely as to the presence or absence 

 of this or of silicate minerals other than those mentioned. 



Brezina 8 classified the meteorite as a crystalline chondrite and gave the following obser- 

 vations upon it: 



This mass shows an amalgamation of granular and crystalline characteristics; the groundmass is porous and has 

 the shimmering appearance of crystalline chondrites (Ck). The globules, as much as 6 mm. in size, are very abundant, 

 and for the most part remain whole, but some are broken in two and stand out sharply against the groundmass. The 

 color of the stone is quite a deep gray on the fresher portions, verging upon the rust brown of the altered substance 

 toward the outer surface. 



BIBLIOGRAPHY. 



1. 1893: Ho WELL. Beaver Creek Meteorite. "Science," July 21, 1893, p. 41. 



2. 1893: BREZINA. TJeber neuere Meteoriten (Niirnberg), p. 162. 



3. 1894: HOWELL. Beaver Creek Meteorite. Amer. Journ. Sci., 3d ser., vol. 47, pp. 430-431. (Illustration of stone.) 



4. 1894: HILLEBRAND. Idem. pp. 431-435. 



5. 1894: MERRILL. Idem. p. 435. 



6. 1895: BREZINA. Wiener Sammlung, p. 260. 



BELLA ROCA. 



Durango, Mexico. 



Here also La Bella Roca and Papasquiaro. 



Latitude 24 55' N., longitude 105 25' W. 



Iron. Fine octahedrite (Of) of Brezina; Rocite (type 14), of Meunier. 



Described 1889. 



Weight 33 kgs. (72. 6 Ibs.). 



This meteorite was found on a peak of the Sierra de San Francisco, called La Bella Roca, 

 near Santiago Papasquiaro in the State of Durango, Mexico. The date of its discovery 

 and the name of the finder are unknown. The meteorite was first described by Whitfield, 1 as 

 follows : 



The two greatest dimensions of the mass were 24.13 cm. by 34.92 cm. 



A feature of the composition of the mass was the presence of large deep pittings on one side; these were a little 

 greater in diameter just below, than immediately at, the surface, and each one had a little substance left on the bottom, 

 which evidently was the remains of what originally filled the cavities. As the analysis shows, this material was troi- 

 lite (FeS 85.27, Fe 9.37, NiS, 2.13). 



The exposed surface of the troilite was greatly decomposed, and gave ground for the idea that the deep pittinga 

 were formed by the removal of troilite nodules, partly while the mass was hot and partly by the subsequent weather- 

 ing. There were nodules of troilite throughout the entire mass of the meteorite, but none were removed so as to form 

 pittings on any other "part of the surface but the side which is supposed to have been the front. The mass was deeply 

 furrowed and all the furrows trended away from the side containing the pittings. 



Slices of the meteorite, when etched, showed rather coarse Widmannstatten figures and also dark- diagonal 

 bands of troilite. 



Analysis by Whitfield gave the following result: 



Fe 91. 48 



Ni 7.92 



Co 0. 22 



C '. . 0. 06 



P 0.21 



S 0. 21 



100. 10 







Whitfield also analyzed the inner and outer portions of a troilite nodule, the results being 

 as follows: 



Inner portion. Outer portion. 



NiS 2.13 2.07 



FeS 85. 27 37. 51 



Fe 2 3 37.80 



H 2 19.85 



Fe 9.37 



96. 77 97. 23 



