METEORITES OF NORTH AMERICA. 181 



the rock. In thin sections, Emmet County, Logrono, and Sierra de Chaco give the same results, with this peculiarity, 

 consequent upon the former, that the transparency of the rock is the less the longer the time since its fall. 



The principal minerals in the Emmet County meteorite are: 



Olivine in very large crystalline masses, showing in polarized light the most brilliant mosaic colorings. In natural 

 light they are colorless, often cloven, and filled with crystalline inclusions. Liquid bubbles, remarkable for then- 

 large size, may also be seen in the spheroidal cavities. In converging light the crystals give two systems of very bril- 

 liant rings whose axes are very remote. 



Bronzite, in crystals poorly terminated, distinctly dichroitic, often presenting rectilinear cleavages parallel to 

 one another and very distinct. 



A m in eral in large crystals slightly colored and having a contrary effect upon polarized light. The action of 

 acids upon them would indicate that they result from the union of alternate lamina} of extremely thin bronzite and 

 olivine, and this supposition may perhaps account for the analysis, published by Smith, of a mineral which he calls 

 peckhamite and which he found in the Esthcrville meteorite. A small fragment of peckhamite in the Museum at 

 Paris shows the characteristics of the new mineral; and a grayish grain, embedded in the specimen 2Q.414 of the Sierra 

 de Chaco meteorite, appears to be identical with this peckhamite. This is another link between the Estherville and 

 Sierra de Chaco meteorites. 



Pyrrhotine, a grain of which shows several faces of the prism. 



Schreibersite, the presence of which is established in the Estherville mass and which shines with a lively luster 

 in the residuum left by the action of acid upon the rock. 



Iron oxide in very distinct octahedrons. 



Nickel-iron. 



It is known that besides the large masses, the fall of May 19, 1879, furnished an abundance of quite complete 

 small meteorites. They differ very much among themselves; some are almost entirely metallic and present a structure 

 resembling that of the syssiderites of the Rittersgriin group. The iron is malleable and yields beautiful etching 

 figures; 8 per cent of nickel has been found in it. Other complete specimens are both metallic and stony. The iron 

 sometimes constitutes an extremely fine network, quite comparable to that of the meteorite of Lodran. 



In view of these various characteristics of composition and structure, it is evident that the identity of this speci- 

 men with the logronite already described is complete. We may suppose, in regard to Estherville, that the original 

 mass was in a fragmentary state, partly stony, partly metallic, perhaps accumulated in a crevice, and was there sub- 

 jected to metalliferous emanations whose product, in the form of a fine network, cemented these independent elements. 

 The remarkable cavities sometimes occurring between the grains of iron and their stony matrices have been artifi- 

 cially reproduced in experiments on the metallic cementation of the powder of peridot by a process previously 

 described. 



Tscherniak u gave a study of the optical characters, as follows: 



The meteorite of Estherville, which brought to the earth many small and some large individuals, may be included 

 among the mesosiderites. Many of the small pieces are composed wholly of iron, others of silicates, the remainder 

 have both. In the larger individuals both occur. If all the masses were united into one, a coarse, irregular mixture 

 of iron and granular silicates would be formed. According to Smith the iron also occurs in the form of nodules among 

 the silicates. * * * In thin sections a green, granular mass is seen, except for the largo crystals of olivine, in which, 

 as groundmass, occurs fine granular olivine with many inclusions in which are suspended crystals and grains of bronz- 

 ite. The bronzite has in part the usual appearance and contains few inclusions, and in part is clouded by fine dust 

 and shows in addition larger glass inclusions. These turbid grains have megascopically an unusual appearance. 

 They have a greasy luster and by the clouding appear brighter than the other constituents. Smith investigated these 

 grains specially and found their composition one of two-thirds bronzite and one-third olivine. He regarded them a 

 special substance to which he gave the name peckhamite. Through the kindness of N. H. Winchell, in Minneapolis, 

 I obtained a specimen of the silicate mixture with some of the lustrous grains, also a large grain of peckhamite. The 

 latter showed the prismatic cleavage of bronzite, but gave also cleavages which could be referred to the crystal faces 

 of olivine. The optical characters were almost similar to those of bronzite. A section parallel to a prismatic cleavage 

 gave the appearance shown. The whole section is clouded by a fine dust and also contains larger inclusions of two 

 kinds. One variety is in the form of dark-brown to black spheres, the other rodlike or spindlelike light-colored glass 

 inclusions which correspond to negative crystals and similarly colored round glass inclusions. A glance suffices to 

 show that the substance is a mixture, and the analysis does not give a result which corresponds to a simple mineral. 

 Since the turbid bronzite in the silicate aggregate shows the same characters as the above-described peckhamite, and 

 since all gradations occur from pure bronzite to peckhamite, I consider this a bronzite which has been rendered 

 turbid and of greasy luster by a great quantity of inclusions. In many places, in sections, one may recognize colorless, 

 transparent crystals and groups of plagioclase which exhibit broad twinning lamellae, now free from inclusions, now 

 again containing crystallized inclusions like the mass of Sierra de Chaco, and now rendered turbid by many small, 

 round glass inclusions. A figure shows plagioclase intergrown with olivine and bronzite. Troilite and chromite 

 occur in grains everywhere in the silicates. 



It will be seen from the above that Tscherniak does not regard Smith's peckhamite as a 

 separate species, and this opinion has been generally concurred in. 



