430 . MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XTTT. 



SURPRISE SPRINGS. 



Near Bagdad, San Bernardino County, California. 

 Latitude 34 33' N., longitude 115 48' W. 

 Iron. Medium octahedrite (Om), of Brezina. 

 Found 1899. 

 Weight, 1,524 grams (3 Ibs.). 



This meteorite was first mentioned by Rust 1 but was described only by Cohen, 2 as follows: 



According to Professor Ward, this iron was found in the summer of 1899, by D. J. Hayes, lying free on the sur- 

 face of a quartz outcrop at Surprise Springs, on the south slope of the Bullion Range, about 45 km. southerly from 

 Bagdad (San Bernardino County), in southern California. The assayer, J. Reed, in San Bernardino, cut for testing 

 a flat piece from the end and determined that upon etching it produced beautiful Widmannstatten figures. 



For closer investigation, I obtained a flat end piece of 157 grams weight, with a section surface of 33 sq. cm. 

 (apparently the piece cut off by Reed), as well as a plaster model of the whole meteorite. 



According to the model, the meteorite had the form of an abruptly truncated, slightly self-renewing cone, whose 

 base and apex were arched like a condyle. Peripherally, there are two concavities nearly the full height of the mass, 

 one of which is smooth and of a shallow shell shape, the other more deeply concaved and having an irregularly pitted 

 surface. It seems that two chips were pried off here, but at a time when the meteorite still had a powerful momen- 

 tum, since according to the model a complete incrustation took place. With the exception of the pitted surface of 

 the large concavity the remaining exterior surface has only such small and shallow pittings that they do not show on 

 the model or on a photograph. The characteristic finger-mark impressions and saucerlike pittings are entirely wanting. 



The thin black crust covering one side of the section is apparently the original fusion crust, which, however, can 

 not be entirely fresh, since it makes a reddish-brown streak, not a black one like the unchanged crust. Where it is 

 entirely or even only in part rubbed away, the structure composed of octahedral lamellae is plainly discernible. From 

 the state of preservation of the exterior the fall may have taken place not long before the finding of the meteorite, 

 unless, indeed, in the region in question, like that of West Atacama, atmospheric precipitation is almost entirely 

 wanting, and a meteoric iron could keep almost unchanged for a long time. 



Immediately upon weak etching, a zone of alteration becomes distinctly visible, which is from 2.5 to 7 mm. 

 broad upon the surface of a section. In reality the breadth may be nevertheless fairly uniform and, indeed, 2 to 3 

 mm. Since the section under consideration is taken from a very slightly arched portion of the meteorite, and the 

 exterior was accordingly cut through at both ends at a very acute angle, the zone shows very much broader here than 

 its actual thickness warrants. On one side, where the zone becomes very small a thin chip has apparently been 

 forced off, but at a time when the heat was sufficiently great to cause an alteration of structure, even though only to 

 a slight depth. That the effect of the heat is confined to a comparatively small peripheral zone, may be explained by 

 the fact that the meteorite upon entering our atmosphere possessed a comparatively low temperature and suffered a 

 high degree of fusion only upon the exterior, and in consequence of its short duration, despite its intensity and the 

 good conductor furnished by the nickel iron, could not spread to the interior. The existence of a zone of alteration 

 also confirms the conclusion drawn from the condition of the surface, that no material change of form took place after 

 the fall of the meteorite. 



The kamacite is very rich in closely compacted etching lines and pittings, so that the etched surface, in conse- 

 quence of the great diffusion of the reflection, appears dull, as is usually the case; yet the oriented luster is still quite 

 distinct. The nongranular bands are in part long and then mostly notched, in part short and swollen. Taenite is 

 well developed. Of the numerous fields, the larger are densely filled with combs. A few small ones are fine grained 

 and very dark, as is usually the case. 



Although the zone of alteration is distinctly divided from the inner portion of the meteorite, the structural altera- 

 tions are comparatively small. The kamacite and the plessite show no intermingling, and accordingly the bands 

 are still well defined. But the latter show neither etching lines nor etching pittings, but upon weak etching appear 

 closely filled with small dark grains, and accordingly have a darker luster, from dull to weak in tone. After stronger 

 etching the kamacite becomes still darker and finally breaks up into fine granules. 



Of accessory constituents, there is only a moderate amount of schreibersite to be mentioned. It appears sometimes 

 as small grains which lie in the bands, and sometimes as plates 2 cm. long by 1 mm. thick. 



Surprise Springs lies on the boundary between medium and broad octahedrites, but may be reckoned with the 

 former. From the fact that a few lamellae of swollen form and irregular outline are found in the section surface, the 

 texture as a whole makes the impression of a coarse structure. 



Analysis: 



Fe Ni Co Cu Cr S P C Cl 



91.01 7.65 0.89 0.07 0.04 0.08 0.22 0.02 0.02 =300.00 



Mineralogical composition: 



Nickel iron '. 98. 33 



Nickel-iron phosphide 1. 43 



Troilite 0. 10 



Daubreelite 0. 10 



Lawrencite 0. 04 



300. 00 



