NOTES ON THE METEORITE OF ESTHERVILLE, IOWA, 

 WITH ESPECIAL REFERENCE TO ITS INCLUDED 'TECK- 

 HAMITE" AND PROBABLE METAMORPHIC NATURE. 



By George P. Merrill, 



Head Curator of Geology, United States Ncitiomil Museum. 



This meteorite, both on account of its unusual Kthological nature 

 and the number of individuals composing the fall, has been the sub- 

 ject of numerous papers and much study. 



It v>^ill be recalled that the first description was by Prof. S. F. Peck- 

 ham/ who briefly noted that the stony portion consisted of dark 

 green crystalline m.asses some of which "are two inches in thickness 

 and exhibit a distinct monoclinic cleavage." This mineral he did 

 not further identif}^, but stated that thin sections of the stone under 

 the micrsocope showed the presence of olivine and a triclinic feld- 

 spar embedded in a matrix of pyroxene. Shepard^ noted the occur- 

 rence of chrysolite in large masses, somic showing imperfect crystal- 

 line facets and an eminent cleavage. He also noted a "feldspathic 

 mineral, presumably anorthite" and an "opal-like mineral of a 

 yellowish brown color, probably chassignite." No mention was made 

 of any pyroxenic constituent. Smith's investigations^ were much 

 more elaborate. Ho determined the presence of bronzite and olivine, 

 the latter in masses "of from one-half to one inch in size, having 

 an easy cleava,ge, especially in one direction." He also examined 

 the opalescent silicate mentioned by Shepard, and by analysis found 

 its com.position as in column I on the next page, which is, he said, 

 "equivalent to SiRo + SjiR, or one atom of bronzite plus one atom 

 of olivine, a form of silica that we maght expect to fuid in meteorites." 

 In a second paper he announced a further investigation of the opales- 

 cent silicate, which he described as having a dingy yellow color 

 and a fused surface. Wlien broken it showed a greasy aspect, with 

 a more or less perfect cleavage and a structure differing widely from 

 olivine. A second analysis yielded as in column II. 



1 Amer. Journ. Sci., vol. 18, July, 1879, pp. 77-78. 



' Idem, vol. 18, Sept. 1879, pp. 18&-188. 



3 Idem, vol. 19, 1880, pp. 459-463, aud 495; vol. 20, 1880, pp. 136-137. 



Proceedings U. S. National Museum, Vol. 58— No. 234!. 



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