422 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 52. 



details such as to warrant referring them to a separate fall, but further study has led 

 to the belief that the stone is a breccia, though the structural variations may be in 

 part due to weathering. 



When the possibility of brecciation was realized, the smallest (870-gram) fragment of 

 the first find was cut in halves and polished. The resultant surfaces showed a ground 

 of about equal parts light gray, mainly oxidized to reddish, and darker gray more or 

 less angular areas. Both portions are equally injected with small, but abundant points 

 of metallic iron and iron sulphide. There are also occasional light-gray fragments, 

 some 2 to 4 mm. in length, which are e^ddently pjrroxenic. To the unaided eye both 

 portions are chondritic, though this structiu-e is much more pronounced in the dark 

 areas. It was at first thought that this difference might be merely apparent and due 

 to the obscuring of the structure in the lighter portions through oxidation. Further 

 investigation has, however, shown that this conclusion will not hold. Under the 

 microscope the lighter portion is chondritic and consists wholly of olivine and ensta- 

 tite with the metallic iron and iron sulphide. None of the twin pyroxenes so char- 

 acteristic of the dark portion, which was the material described in the first part of this 

 paper, are present. Further than that, the chondrules in the light portion are almost 

 wholly very light gray and nearly white, while those in the dark portions are in part 

 of a dark-gray color, although there are white chondrules here also. By reflected light 

 the polished surface shows a structure distinctly brecciated, and in one or two cases 

 it is possible to trace the outlines of a fragment of the darker rock inclosed in the lighter 

 gray, but in the majority of cases this is impossible, and the darker material is so com- 

 mingled with the lighter that for a long time considerable uncertainty existed in the 

 mind of the writer as to the true nature of the stone. Even now he confesses to not 

 feeUng fully satisfied, but until one of the larger masses of the new find can pass into 

 the possession of the Museum and be sawn through the center, in the hopes of getting 

 beyond the zone of oxidation, this is the best that can be done. The strongest argu- 

 ment in favor of the brecciated nature of the stone seems to lie in the presence of the 

 polysynthetically twinned pyroxenes in the dark-gray chondrules and their absence 

 in the lighter portions. In one instance the line of demarkation between the Light 

 and dark portions could be plainly traced in thin section, and the metallic sulphides 

 were found elongated along this line to indicate that it had been an open cleft at the 

 time of their deposition. 



In a single instance, in a radiating enstatite chondrule, there was noted a few minute 

 inclosures of a blue-green mineral the like of which the writer has never before seen 

 in a meteorite, and the exact nature of which can not be determined. The particles 

 show no good crystal outUnes nor cleavages such as would enable one to determine 

 their orientation, optic axes, or extinction angles, and, except that they belong appar- 

 ently to some inclined system, nothing can be said. The mineral is scarcely trans- 

 parent and but faintly dichroic in yellow-green colors. More than anything else that 

 can be recalled, it resembles the green hornblende inclosures sometimes found in 

 pyroxenes in the older basic igneous rocks. In all the thin sections thus far prepared 

 the mineral occm-s in but a single instance. 



So far as now known the total number of individuals comprising the Plainview fall 

 is nine (including the two fragments), and the total weight 24,112 grams. 



