146 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



COSTILLA. 



North side of Costilla Peak, Sangre de Cristo Range, Taos County, New Mexico. 

 Latitude 36 55' N., longitude 105 3(X W. 

 Iron. Medium octahedrite (Om) of Brezina. 

 Found 1881; described 1895. 

 Weight, 35 kgs. (78 Ibs.). 



This meteorite was described by Hills * as follows : 



This meteorite, which for several years has been in the possession of the society, was found in August, 1881, on 

 the north slope of Costilla Peak, about 6 miles south of the boundary line between Colorado and New Mexico. The 

 date of the fall is unknown. The disco verer/was a Mexican sheep herder named Ignacio Martin, who the same year 

 sold the specimen to an old settler, one Thomas Tobeus, receiving in exchange a small pony. Tobeus kept the speci- 

 men for several years concealed under a manure pile in his barn, until Mr. E. C. van Diest, hearing of its existence 

 and recognizing its true character, purchased it for the society. According to Mr. van Diest, to whom the writer is 

 indebted for these particulars, it is impossible to obtain more specific information in regard to locality and occurrence, 

 for the reason that Martin and his associates entertain the belief that the mass is native silver derived from a rich lode 

 somewhere in the vicinity of the find, and they are naturally desirous of discovering and locating the bonanza them- 

 selves. Previous to slicing, the dimensions of the mass were: Length 32 cm., breadth 23 cm., thickness near center 

 10 cm. The weight on platform scales was approximately 78 pounds. When viewed in the direction of the shortest 

 diameter, the outline is roughly rectangular. Of the two principal faces, one is rounded and comparatively smooth; 

 the other, if anything, slightly concave with deep flutings and cavernous depressions. Two of the adjacent edges are 

 comparatively thin and beveled. Of the other two, the longer exhibits a series of deep grooves, rudely parallel with 

 the short diameter of the mass, though preceptibly divergent; the shorter has a smooth, facet-like termination. The 

 well-preserved surface shows the fine strise usually ascribed to the flow of the metal while passing through the 

 atmosphere. 



The etched surface shows the crystalline structure, which is approximately parallel with the direction of the octa- 

 hedral cleavage. The kamacite bands are from 1 to 2 mm. in width and of considerable length. The taenite lines, 

 which are irregular in trend and direction, are of capillary size and only visible through a lens or in strong reflected 

 light. Here and there are small nodules of troilite, from 1 to 10 mm. in diameter, some of which inclose a dark-gray 

 substance resembling graphite. The etched surface is traversed by prominent irregular cracks, roughly following 

 the planes of cleavage, some of which inclose a black substance resembling graphite. 



Analysis by Mr. L. G. Eakins: 



Fe Ni Co P S 



91.65 7.71 0.44 0.10 0.26 =100.16 



Mr. Eakins says: "The sulphur of course indicates the presence of troilite, which was plainly visible in the piece 

 sent to me, and would be equivalent to one-half of 1 per cent of this substance. The phosphorus is derived from the 

 schreibersite which was evidently present, being noticeable as the iron was being dissolved." 



As the sample contained one of the larger nodules the troilite is probably less than is estimated by the analyst. 



Brezina 2 says of Costilla: 



Costilla Peak shows, on a plate cut through the whole mass, beautiful orientation of the surface; the convex edge 

 face, plainly belonging to the front side, shows traces of the somewhat rusted, thin front crust along which runs a 

 glimmering alteration zone 2 to 5 mm. thick. The concave opposite side shows a rear side crust 0.5 to 2 mm. thick, at 

 the thicker points concentrically layered, and an alteration zone 1 to 9 mm. thick. The lamellae are long, straight, 

 grouped, 0.8 mm. thick, the tsenite weak, fields predominant, mostly containing repetitions of the lamellae. The kama- 

 cite and fields are granular; the former coarse, the latter fine. There are many troilite grains and plates distributed 

 through the whole mass. Great similarity with Independence. 

 The meteorite is distributed. 



BIBLIOGRAPHY. 



1. 1895: HILLS. The Costilla Meteorite. Proc. Colorado Sci. Soc., read January 7, 1895. (Illustrations and analysis 



by Eakins.) 



2. 1895: BREZINA. Wiener Sammlung, p. 280. 



Couch Iron, see Fort Duncan. 



