300 Field Columbian Museum — Geology, Vol. I. 



4. In structure it belongs to the class of crystalline chondrites. 



5. In chemical composition it is made up chiefly of oxides of 

 silicon, iron, magnesium and chromium, with small percentages of 

 iron, nickel, sulphur and minor constituents. 



6. Its mineralogical composition may be estimated as 47% 

 bronzite and some monoclinic pyroxene, 25% chrysolite, 9% chro- 

 mite, and the remainder nickel-iron, troilite and schreibersite or alter- 

 ation products of these. The content of chromite is remarkable and 

 the highest yet reported in meteorites. 



NESS COUNTY, KANSAS. 



MUSEUM No. Me. 490. 



Of this fall the Museum possesses one small complete individual 

 having a weight of 85 grams. This aerolite in general form is wedge- 

 shaped with angles but little rounded. Except for one fractured sur- 

 face it is covered with a black crust or one which was undoubtedly 

 originally all black, but through weathering has taken on in places a 

 rusty brown appearance. The crusted surface is smooth but uneven, 

 the irregularities suggesting pitting, although the depressions are not 

 deep enough to produce pits of definite form. On making a section 

 through the stone and polishing the surface thus exposed, the crust 

 appears as a distinct black border having a thickness of about ^ mm., 

 in contrast to the dark brown color of the interior of the stone. In 

 texture the crust does not differ noticeably from the interior, the po- 

 rosity of many meteorite crusts not being in evidence. The dark 

 brown color of the interior of the stone is doubtless largely a discolor- 

 ation due to weathering. So completely has this discoloration 

 penetrated the stone that it is impossible to find a place where 

 the probable original color remains. The discoloration also makes 

 it impossible to make out much regarding the structure of the 

 stone megascopically, chondri not being visible on a polished surface. 

 Metallic grains are numerous over the polished surface. They are 

 for the most part of small size, the largest that I have noticed not 

 being over 1 mm. in diameter. They consist both of nickel-iron and 

 troilite, the grains of the latter being distinguished by their yellow 

 color and by not taking on a deposit of copper when immersed in 

 copper sulphate. These troilite grains are quite as numerous as the 

 grains of nickel-iron, but never as large. 



In texture the stone is compact but it is only fairly coherent, 



