SIDEROLITE. 61 



compact mass of iron, showing onl}- a few small nodules of pyrrhotite. A 

 general description, with figures showing the structure of its etched surface, 

 has been given by Professor J. W. Mallet.* 



A specimen of the Coahuila (Mexico) siderolite in the Harvard Col- 

 lege Mineral Cabinet shows a compact mass of iron, with irregularly distrib- 

 uted elongated cells filled with pyrrhotite. The chief portion of the iron 

 seems to be free from these irregular masses of pyrrhotite, but some parts 

 are quite filled with them. 



The Texas (Gibbs) siderolite in the same collection shows a compact 

 metallic mass, holding a few rounded and irregular cells containing pyrrho- 

 tite. This rock has been de.scribed by Professors Silliman and Hunt, who 

 also give a plate representing the Widmannstattian figures.! 



The specimen of the Butler (Bates Countv, Missouiu) siderolite in the 

 Harvard College Cabinet is \ery compact, but contains a few elliptical and 

 irregular cells filled with pyrrhotite (troilite) surrounded by rings. These 

 rings connect with the raised bands shown by etching. " Some of the bands, 

 indeed, appear as oflshoots from the rings. In this specimen the etching has 

 not brought out the Widmannstattian figures very clearly, yet the above 

 relations can be distinguished. A brief description of tliis siderolite was 

 given by Professor J. Lawrence Smith, with analysis of the iron alone. The 

 nodules of troilite, according to him, were numerous, but free from any 

 schreibersite. In his specimen the Widmannstattian figures were readily 

 developed and found to be large and regular, t 



Some siderolites like that from Toluca, Mexico, in the Harvard College 

 Cabinet are composed of a very coarse sponge-like mass of iron, holding 

 detached irregular masses of pyrrhotite, etc. In this the distance across the 

 iron from one cell wall to another cell wall is greater than the diameter 

 of the cells themselves. 



The general structure of the meteoric form may then be said to be a mass 

 of iron, or of iron inclosing more or less irregular and nodular masses of 

 pyrrhotite, schreibersite, graphite, etc. 



Associated with the meteoric iron, in intimate union with it or in com- 

 binations of their own, occur nickel, cobalt, magnesium, aluminum, calcium, 

 silicon, chromium, phosphorus, copper, carbon, arsenic, sulphur, tin, mangan- 

 ese, potassium, sodium, chlorine, oxygen, beryllium, etc. 



* Amer. Jour. Soi., 1871 (3), ii. 10-15, 1878 ; xv. 337, 338. 

 t Am. Jour. Sci.,18i() (2), ii. 370-376. 

 i Am. Jour. Sci.,1877 (3). xiii. 213. 



