METEORITES OF NORTH AMERICA. 445 



According to Martius, jr., its analysis is as follows: 



Fe 89. 22 



NiCo 9. 51 



P 0. 20 



Schreibersite 0. 06 



C. and white mineral 0.24 



99.23 

 Rose 20 described an occurrence of quartz in Toluca, as follows: 



Nagel, in a specimen of the Xiquipilco iron in his distinguished collection, recently observed a small crystalline 

 point jutting out through the oxidized crust, which upon freeing it a little more, appeared as a four-faced projection 

 with glistening surfaces. This he brought to me for closer examination and determination of the embedded crystal, 

 and permitted me to remove the crystal from the brown iron oxide and preserve it in the Royal Museum. A small 

 fragment of another crystal, which stuck beside this one in the crust, but which was broken in the removal, Nagel 

 also gave me for investigation. 



When the crystal was removed from the matrix it left a smooth-faced impression. It was only one-third line in 

 size, yet, despite its smallness, not only could its form be determined as that of a hexagon-dodecahedron, but even 

 its angles could be measured with considerable exactness. These angles were 103° 35.40', 103° 25.49', and 133° 30.42'. 

 In the case of quartz the same angles measure 103° 34' and 133° 44'. The crystal is accordingly quartz, and likewise 

 the broken fragment of the crystal which was embedded near the former, since before the blowpipe it melted to a clear 

 glass. 



Moreover, quartz crystals are seldom found in the sand, and quartz sand is probably not present at all in the 

 Toluca region, since the surrounding mountains are composed of a quartzless trachyte or recent volcanic stone. 



I also found small quartzlike grains upon the exterior of another Toluca iron, but unfortunately they were lost. 

 The quartz crystals appear to occur only very seldom on the Toluca irons. 



Reickenbach 21 gave tbe following further observations : 



Toluca gives the only case I know of in which a fusion crust collected pure and remained observable after many 

 years. I have a meteoric-iron mass of the size of my fist and of a flattened cubic form in my collection from the valley 

 of Toluca in Mexico. One large side had a rusty, scaly crust, like all old iron meteorites, the other on the contrary, 

 although it had the same rusty color, did not consist of iron at all, did not resemble a meteorite at all in fact, but a dried 

 mass of clay. It was full in all directions of crooked cracks under one-third of an inch in depth and was very hard, 

 brittle, and sharp-angled. Nitric acid did not attack the polished surface of a detached fragment; a piece of fresh 

 slag treated in the same way manifested the same appearance and the same behavior toward reagents, therefore the 

 clayey mass is compacted fusion-crust material. Its agglomeration must have taken place in a peculiar way. The 

 iron mass had received in falling, whereby it was broken into many pieces, a deep crack wide enough to lay one's finger 

 in. In this crevice molten-crust material accidentally accumulated, filled parts of it completely, and upon cooling 

 therein became a crooked hollowed old slag. The fracture of the half-severed piece is still distinctly visible. This 

 fine enamel in several polished pieces is clear as crystal, dark brown, scratches glass, contains here and there scales of 

 fine threadlike iron crystals, and is, within my knowledge, the only known example of a well-preserved molten 

 meteoric-iron crust. 



The yellowish-white iron sulphide is found well marked in Xiquipilco. Indeed, this iron meteorite contains, in 

 predominant quantity, the equally well-marked bronze-colored iron sulphide, magnetic pyrites; the third form also 

 occurs, the yellowish-white, and is clearly distinguished from the closely associated bronze-colored variety. Its 

 individuality is not readily discerned when it occurs alone, but here it occurs with and in immediate proximity to the 

 bronze-colored variety. Indeed it surrounds and incloses the latter, forms the transition member between the bronze- 

 colored iron sulphide and the Trias, and spreads out farther in the latter. In the latter it forms specks and maintains 

 its distinction in color from both the others. 



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Graphite is found more or less abundantly in lumps ranging from the size of a pea up to that of a walnut in Istlahuaca 

 and Ocotitlan. 



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Graphite occurs as an accompaniment of magnetic pyriteB in the case of Xiquipilco and in an especially well-marked 

 degree in that of Ocotitlan. 



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Graphite occurs in lumps 2 inches in diameter embedded in the midst of the iron in the case of Ocotitlan. 



I have a specimen of the Toluca iron about the size of a small fist which shows an excellent illustration of iron-glass 

 in considerable quantity, lying in a wide-open crevice and largely filling the same. 



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Iron-glass occurs in a crack of Ocotitlan interlaced with the bands of kamacite and penetrating them. 



