0. C. Farrington — Analysis of "Iron Shale" 303 



Art. XXVII. — Analysis of "Iron Shale" from Coon Moun- 

 tain, Arizona ; by Oliver C. Farrington. 



In the account recently published by Messrs. Barringer and 

 Tilghnian* of their investigations at Coon Mountain, Arizona, 

 they call attention to a magnetic oxide of iron, locally known 

 as " iron shale," which they state occurs in considerable quan- 

 tity upon the mountain. The distribution of the shale is 

 stated to be around the rim of the " crater," especially on and 

 in its northern portion and near by on the plain. In the form 

 of minute particles, either as fragments or as spherules, it is 

 also said to occur over the surface of the surrounding country 

 concentrically around the crater for perhaps several miles. 

 Beneath the surface large fragments are found, at varying 

 depths, the greatest depth noted being twenty-seven feet. 

 The pieces reported by these authors varied from one to thirty 

 pounds in weight. !No quantitative analysis of the shale is 

 given, but qualitatively it is said that all the specimens 

 examined contained nickel to the same extent, proportionally 

 speaking, as in the Canyon Diablo meteoric iron. It is also 

 stated that within the larger pieces may be seen green hydrox- 

 ide of nickel, while in the very minute pieces of shale the 

 nickel has leached out to a greater or lesser extent. Occurring 

 with the shale and believed by these authors to be related to 

 it, are so-called u shale balls," which are described as roughly 

 globular to oval in shape, the outside having been converted 

 into hydrated oxide of iron, while the interior is usually 

 magnetic oxide of iron. These are said, when broken open, 

 to show in nearly every instance the green hydroxide of 

 nickel. In some cases these shale balls are said to contain a 

 solid iron center. As the magnetic oxide which surrounds 

 this center usually presents a more or less laminated appear- 

 ance, it is assumed that the so-called iron shale found on the 

 surface, as seen on a slightly curved piece, has resulted from 

 the alteration of the shale balls. It is also stated that the 

 pieces of laminated oxide are often grouped, as if a shale ball 

 or piece of meteoric iron which was once covered by a mag- 

 netic oxide of iron had fallen on the spot and the magnetic 

 oxide of iron had been disintegrated by the fall, or afterward 

 by atmospheric agencies. These authors apparently consider 

 their mention of this material the first which has been pub- 

 lished, but in Foote's account of the Canyon Diablo meteor- 

 itesf mention is made of material which is probably of the 



*Proc. Phila. Acad. Nat. Sci., vol. lvii, pp. 861-914, 1905 ; this Journal, 

 June, 1906, p. 402. 



f This Journal (3), vol. xlii, pp. 413-417. 



