130 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Later, Smith ls , " made the Butcher iron the subject of further investigation. In 1876, he described an incrus- 

 tation of aragonite upon two blocks, and a new mineral, which occurred mixed with troilite, both surrounding and 

 penetrating it. He considered it a ferric compound of chromium and sulphur (CrS) and proposed the name daubr^e- 

 lite for it. When two years later he found, upon a section surface measuring 1,800 sq. cm., about 30 troilite nodules 

 of -ff mm. in diameter, all of which were penetrated by the mineral in question, he succeeded in securing pure ma- 

 terial in considerable quantity*. He obtained this time the percentages from which the formula, FeS. Cr^a was derived. 

 In 1881, he 18 found an oval lump of chrome iron 17 by 12 mm. in size, with 62.71 per cent Cr 2 O 3 , 33.83 per cent FeO, 

 traces of Co, and a few included silicate grains. This was the only large chromite nodule hitherto observed in meteoric 

 iron. 



Daubree 19 observed as many as 70 inclusions of troilite with daubreelite, sometimes roundish in form, sometimes 

 angular, upon a section 800 sq. cm. in size, as well as a cleft extending entirely through the same and filled with 

 magnetite. 



Brezina 2 ? made a series of further investigations. He found in a druse of the otherwise compact iron a crystal of 

 troilite 12 mm. high and of the same thickness, showing the faces 2P(2021)and OP(OOOl) with distinct basal cleavage; 

 the faces of the pyramid were many faceted and scratched near the base. Brezina thereupon came to the conclusion 

 that iron sulphide in the stone and iron meteorites was apparently as little chemically as crystallographically differ- 

 entiated, and that it was in both cases pure iron sulphide. Four plates of daubreelite of 0.2 to 6 mm. in thickness 

 were inserted in the troilite crystal parallel to the base, and it is supposed that in the remaining noncrystalline troilite 

 there is the same regular orientation of the daubreelite. He further noted the occurrence of the troilite in the form of 

 Reichenbach lamellae, which attained a length of 10 cm. and was always surrounded by a granular zone 1 to 1.5 mm. 

 wide. Also where short, straight little troilites accumulate the whole mass is surrounded by an area in which etching 

 lines are almost entirely wanting. In the same year Brezina described a peculiarly wrinkled parting face extending 

 through the entire block along which, upon cutting, a division appeared. In 1885 he 26 united the Butcher iron and 

 Santa Rosa with Saltillo; in 1895 he 47 separated the latter and placed it with Fort Duncan. Finally he mentioned a 

 piece the size of a fist consisting of a hollow body with included nodules which showed outer crust and pittings 

 meeting in a sharp ridge. 



In 1884 punier 24 referred "Coahuila" to his Caillite group whose other representatives were distinguished by 

 peculiarly beautiful Widmanstatten figures. In 1893 he " formed a distinct group "Coahuilite" for Coahuilin 

 characterized by 4 per cent of nickel and, in comparison with Braunin, of different grain and color, less solubility in 

 acid, and absence of rhabdite. Santa Rosa (1850), on the contrary, he describes as consisting of Braunin with rhab- 

 dite. In 1886 Huntington 30 stated that the etching lines of Coahuila are distinguished, under the microscope, from 

 Widmannstatten figures, as they show for example in Butler, only by greater fineness; besides hexahedral cleavage, 

 octahedral also occurs, and the etching lines run parallel as well to the edges of the cube as to those of the octahedron. 

 Between irons with typical Widmannstatten figures and those with Neumann lines all gradations are in his opinion 

 present. In the following year he 33 determined the specific gravity of 10 different specimens of the same block and 

 obtained between 7.204 and 7.867. He concluded from the figures obtained that one could not, as Hidden had done, 

 depend upon specific gravity to distinguish meteoric irons. This is self-evident indeed when one considers the irregular 

 distribution of the subsidiary material even if, in the other experiments, material free from foreign substances was 

 employed for the determinations. Judging by the above large differences this seems not to have been the case in a 

 single instance. 



In a further work Huntington 35 made the observation that the Butcher iron is distinguished by small, plane, 

 brightly glistening faces of at most 10 mm. in size, which may be compared to interpenetrating twins of two hexahedrons 

 and which show a very distinct striping parallel to the sections of all the faces. Since Sanchez Estate, relative to its 

 cleavage, behaved otherwise, he thought it could not belong to the same fall, as was formerly held by him. 



Finally Huntington described a large section of the Butcher iron in the Harvard collection which showed very 

 prominent Neumann lines, but also showed Widmannstatten figures upon a band-like area running through the thickest 

 portion of the block. The etched surface of a still larger section of the same block he stated had an appearance com- 

 parable to that of a frosted pane of glass with a crystalline formation increasing from the outside toward the interior. 

 He stated that one could easily obtain sections of smaller circumference which showed only Widmannstatten figures, 

 Neumann lines, or a granular structure. This difference in structure he accounted for by the more rapid cooling of 

 the peripheral than of the central portions. Although large sections of the Butcher iron are tolerably well distributed 

 no similar observation has yet been mentioned. 



Derby 49 was of the opinion that the etching lines observed and described by Huntington correspond in part with 

 his "Bendego lines," that is, they answer to the projection of the faces of a hexakis-octahedron. 



Hartley and Ramage 50 made a spectroscopic analysis of Coahuila. Davison 51 noted 0.0023 per cent of platinum, 

 which was apparently accompanied by iridium. 



Analyses. 



I. Hacienda de Santa Rosa; total analysis by Wichelhaus. The low percentage of Ni, Co is due to precipitation by 



barium carbonate. 

 II. Santa Rosa (Lupton's iron). 



III. Bonanza; Shepard. White grains, as insoluble residue, about 0.01 per cent. Specific gravity, 7.825. 



IV. Butcher iron; Smith. Specific gravity, 7.692. 



V. Daubreelite from Butcher iron; Smith. Specific gravity, 5.01. 



