THE CONSTITUENTS OF METEORITES 40 5 



arranged parallel to the planes of a cube. Lamellae having this 

 arrangement are known as Reichenbach lamellae. Individual 

 lamellae of this sort average from 0.1-0.2'"™ in width and 

 l^-S;^*^™ in length. They cross layers of kamacite, and 

 hence must have formed before these. Troilite often occurs 

 intergrown with schreibersite and graphite, and these sometimes 

 surround it. It also often includes nickel-iron. 



The fusion and dissipation of troilite nodules during the pas- 

 sage of a meteorite through the atmosphere is a cause of the 

 depressions often to be observed on the surface of both iron and 

 stone meteorites. 



ThQ iron sulphide of the stone meteorites occurs chiefly as 

 grains, sometimes as plates, and sometimes in vein-like forms. 

 As mentioned in a previous article, it also occurs in chondri, fre- 

 quently forming their periphery, while at other times it is in the 

 form of grains. Crystals from the druses of the Juvinas meteor- 

 ite measured by Rose proved to be hexagonal and to have forms 

 similar to those of terrestrial pyrrhotite. It is largely on account 

 of these observations that the iron sulphide of stone meteorites 

 is considered to be pyrrhotite. On the other hand, the iron 

 sulphide of stone meteorites differs from pyrrhotite in being, 

 for the most part, non-magnetic, and in giving no free sul- 

 phur on decomposition with hydrochloric acid. Further, most 

 analyses show a composition corresponding to the formula 

 Fe S. 



Schreibersite. — This mineral, peculiar to meteorites (if its pos- 

 sible occurrence in the terrestrial iron of Greenland be excepted) 

 is also one of their most remarkable constituents, since it gives 

 proof that the meteorites in which it occurs could not have 

 been exposed for any long time to the action of free oxygen. 

 The mineral is a phosphide of iron, nickel, and cobalt, having 

 the general formula (Fe, Ni, 00)3 P, though the relative pro- 

 portions of the metals vary. The normal color is tin-white, 

 but this may readily alter to bronze-yellow or steel-gray on 

 exposure to the air. Hardness 6.5, specific gravity 6.3-7.28. 

 Strongly magnetic, and when magnetized retains its magnetism 



