THE METEORIC PERIDOTITES. — LHERZOLITE. 97 



between the columns a cloudy substance was observed. Coben is in doubt whether this 

 sulistance is an alteration-product or has intruded. 



The second is formed from aggregations of round or angular olivine grains and a 

 cloudy substance. The olivine and enstatite also occur in the groiindmass. The enstatite 

 incloses some opaque grains and colorless microUtes. The olivine contains some pores 

 which are for the most part empty, but some of them appear to hold a little fluid. 



Cohen thought that an accessory mineral observed was hypersthene. Pyrrhotite and 

 nickeliferous iron were also seen. Between all these constituents lies a cloudy, very 

 rarely feebly transparent substance which appears to be identical with that observed in 

 the spherules. 



Cohen seems to adopt the mechanical theory for the origin of chondritic structure, 

 but, following Giimbel, holds that the eccentric radiated structure of many of tlie 

 spherules is owing to a secondary formation.* 



Cohen's cloudy substance is doubtless the gray, fibrous, base and semi-base observed 

 by the present writer in other meteorites — like the Iowa one, for instance. 



EsthcfviUe, Emmd Co., Iowa. 



The Estherville meteorite has a grayish granular groundmass, holding irregular grains 

 of olivine and diallage. The olivine grains are of various sizes, from minute ones to 

 those two inches in diameter. Scattered through the mass, in irregular nodular jagged 

 forms, occurs the u'on. Some bluish-gi-ay fragments were seen mclosed, but of an 

 unknown nature, although tliey may be olivine. The groundmass is identical iu appear- 

 ance with that of the finer-grained peridotites, and, excepting the iron, the rock is strik- 

 uigly similar to some from Xorth Carolina. 



Two or three patches composed of yellowish-green olivine, and a glassy white mmeral 

 ■were seen. The latter resembles feldspar or quartz, but it would probably not be found 

 in the section, or by chemical analysis, unless especial portions were taken for examina- 

 tion. The iron shows imperfect dodecahedral forms with striated faces. One imperfect 

 form resembled a cube face modified by two pentagonal dodecahedral planes. A few small 

 black grains were seen resembling picotite or chromite. The crust in some places shows 

 that it was derived from the fused olivine; hence if tlie fusion point of this olivine could 

 be ascertaineil, it would give the minimum temperature of the surface during its passage 

 through the air. The specimen above described, in the Harvard College Cabinet, is said 

 to weigh twenty-eight pounds, and it affords, on account of the large extent of its frac- 

 tured surface, a good opportunity to study the macioscopic characters of this peridotite. 

 This specimen, iu some places, shows the remains of an internal cavernous structure, its 

 cell-walls being lined with minute crystals. 



Section : a grayish groundmass, holding grains of enstatite, olivine, and diallage, with 

 iron and pyrrhotite. The groundmass is composed of a crystalline, granular aggregate of 

 these minerals. 



The oliraie is in clear, rounded grains, of irregular outline. Lying in the ohvine 

 are numerous grains and irregular masses of iron, which are usually confined to certain 

 portions of the mineral, and are wanting in some crystals. Besides the larger, easily 

 recognizable, irregular, semi-sponge-like masses of iron surrounding, projecting into, or 

 included m the olivine, drop-like forms are seen extending in irregular Imes from 



* Verh. Natur. J[ed. Verein, Heidelberg, 1878, ii. (2), 15i-163. 



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