40 BULLETIN 94, UNITED STATES NATIONAL MUSEUM. 



From these results, aided by a microscopic study, the composition 

 of the entire mass has been calculated as follows: 



Per cent. 



Silica (SiOj) .- 37.14 



Alumina (Al=03) 2.15 



Titanic oxide (TiOs) -07 



Ferrous oxide (FeO) 10.45 



Nickel oxide (NiO) .033 



Manganous oxide (MnO) .23 



Lime (CaO) 1.76 



Magnesia (MgO) 23.44 



Potash (KjO) .097 



Soda (Na=0) .79 



Water (H^O) .28 



Phosi3horic acid (P2O5) -25 



Iron (Fe) 15.53 



Nickel (Ni) 1.51 



Cobalt (Co) .09 



Copper (Cu) -006 



Troilite 5.05 



Chromite .77 



Magnetite .16 



99. 806 



The mineral composition is olivine, enstatite, metallic iron, mag- 

 netite, troilite, and chromite, with a lime phosphate and plagioclase 

 feldspar (?) in very small quantity. The proportional amounts of 

 these constituents are: Iron, 17.30; troilite, 5.05; chromite, 0.77; mag- 

 netite, 0.16; soluble silicates (mainly olivine) and phosphates, 37.23; 

 insoluble silicates (mainly enstatite), 39.6G. 



The structure is chondritic and compact ; somewhat friable ; color, 

 gray. 



The 330-gram piece is the gift of Mr. James Hi slop. 



Reference. — E. E. Howell, The Beaver Creek meteorite. (Chemi- 

 cal work by W. F. Hillebrand, microscopic work by Geo. P. Mer- 

 rill.) Amer. Journ. Sci., vol. 47, 1894, p. 430. 



BELLA ROCA, SIERRA DE SAN FRANCISCO, SANTIAGO, PAPASQUIARO, DURAl^GO, 



MEXICO. No. 142. 



Iron, Of. Weight 152 grams. Irregular mass 5 by 6 cm., contain- 

 ing cavity left by oxidation of large troilite nodide; one surface 

 etched, showing Widmanstiitten figures and scattering troilites. 

 Weight of original mass 33 kilograms. Date of fall unknown. 

 Found in 1888. Described by Whitfield, who found the metallic 

 portion to consist of: 



