Εικόνες σελίδας
PDF
Ηλεκτρ. έκδοση
[ocr errors][merged small]

DISCOVERY OF METEORIC IRON IN NEBRASKA.

ERWIN HINCKLEY BARBOUR.

During the author's residence in Nebraska for the past five years he has been on the alert for any specimens of meteoric origin in Nebraska. Until recently, however, he has entirely failed, although "genuine” meteorites have been repeatedly offered for sale at exorbitant prices. One large stone weighing about sixty pounds was offered at a price exceeding $1,000, yet it was nothing more or less than a glacial boulder of Sioux quartzite. The compact and glassy texture of the quartzite boulders, coupled with their purplish color, have led many to attribute their origin to every cause but the correct one. These boulders are neither volcanic bombs, semi-fused and reddened by heat, nor are they meteorites. Though insisting that he ought in all justice to receive $1,000, the owner of the drift boulder in a paroxysm of generosity offered to donate $500 worth of his meteorite to the State Museum providing the State Museum raise the other $500 and donate it to him. Not wishing to carry it with him he left it with the curator of the museum, and it is here still.

The commonest form of meteorite which has been brought to the department for determination is that found in burnt hay and stiaw stacks. It is very common for a sort of glass to be produced by such combustion and the appearance is not unlike what the inexperienced might take for a meteoric stone. Finding such in the ash of a burnt stack, and believing that meteorites are superheated, the popular inference is that the stack was fired by a shooting star and that the solid glassy substance is a real meteorite.

Another fruitful source of meteorites is the concretionary

[ocr errors]

layer in the Dakota Cretaceous. Our Cretaceous is so charged with iron that in many places it has the appearance of a clay semi-fused, or melted into nearly pure iron. Such, at least, is the popular impression of it. It is very common to find throughout this stratum nodules filled with colored sand; sometimes, however, they are solid and ring under the hammer and break like cast iron. These are a source of constant concern to many who think they have found a bed of meteorites. They are repeatedly brought to the department for determination.

At last, however, a genuine meteorite has been found in Ne braska. This is of the pure iron type known as the siderite and weighs exactly 835.2 grams. This was found in 1878 on the farm of Mr. Robt. M. Lytle, near York, Nebr., having been turned up by the plow.

It was found eight inches below the surface in virgin prairie soil and would naturally attract attention from the fact that as far as the author knows no glacial drift or boulders occur in this region. The ground is practically a fine black loamy soil without boulders or gravel. It also attracted Mr. Lytle's attention from the fact that, though small, it was extremely heavy, and on pounding it with a hammer he immediately discovered it was jron throughout, and at once suspected its extra-terrestrial origin. This was kept in the possession of Mr. Lytle until the past summer, when the author secured it while investigating wells in the region of York, in York County. Every indication showed that it was a pure iron meteorite, the dark oxidized surface, the conchoidal depressions, and the absence of angles and edges led plainly to its real identity. Its final determination was easy. After planing and burnishing one small portion of the meteorite, there appeared upon the burnished surface what may be called natural Widmanstätten figures.

There were two sets of lines, the one set dark, rather irregular, and very distinct, the other running at an angle of 80 degrees, fine, but quite visible to the eye. This alone was sufficient determination. However, upon etching the burnished surface with dilute nitric acid, very pronounced Widmanstätten figures were

brought out, exactly coinciding in direction and nearly in position with the lines which naturally occurred there, making it perfectly certain that the first lines noticed were plainly lines of crystallization visible without the intervention of artificial means. The bold lines represented a particular zone, which passed directly through the regularly formed Widmanstätten

[ocr errors][ocr errors][merged small][merged small][ocr errors][merged small][merged small]

region. In all of this zone the lines were completely parallel or nearly parallel to one another, and without any cross lines looking as though there had been some peculiar fault or re-arrangement of the parts at some previous time. Above this zone and below it the Widmanstätten figures were nearly of the ordinary type. See Figs. 4 and 5.

By the courtesy of Mr. George F. Kunz, the writer is able to publish the following analysis of the above meteorite: Iron

87.96% Nickel

7.38% Cobalt

0.74% In Huntington's catalogue of the recorded meteorites, brought down to 1887, there is reported from Fort Pierre, in Nebraska, a meteorite which fell in 1856, consisting of two fragments, weighing respectfully thirty-five and twenty-eight grams, which he

[ocr errors]

numbered in his catalogue 225. This is probably a mistake, for Fort Pierre is in South Dakota, which will leave the Lytle meteorite as the first recoded in the state.

While this notice was going to press a second meteorite, also turned up by the plow, was procured by the author from southwestern Nebraska. This, too, is a pure iron meteorite weighing 2,783.3 grams (6.13 pounds). When etched the Widmanstätten figures appeared but feebly, due possibly to some derangement consequent to the rough handling to which this excellent specimen has been subjected, it having been pounded and battered by a heavy hammer. See Figs. 6 and 7. The University of Nebraska,

December 26, 1896.

Plate VI. Four views of the York county, Nebr , meteorite.

« ΠροηγούμενηΣυνέχεια »