212 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vol.. SO 



steel-gray to nearly tin-white color, quite brittle and strongly mag- 

 netic. Their specific gravity is 7.20, and on analysis gave : 



P iS-370 



Fe 58.540 



Ni 26 . 080 



Co 0.052 



Cu trace. 



The third form of the phosphide is as the lath-shaped form called 

 rhabdite. This form occurs very sparingly free, and not enough of 

 it was secured to do more than make a qualitative test to prove its 

 identity. It is abundant as a constituent of the schreibersite lamellae, 

 and under the microscope, using a vertical illumination, the charac- 

 teristic flat prisms are readily seen. In addition to the above forms 

 of schreibersite, there is left a black non-magnetic residue having the 

 following composition : 



P 8.77 



Fe 84.29 



NiCo 5-00 



C '. 2.16 



Very little can be said concerning this material except that it may 

 be a decomposition product resulting from the prolonged treatment 

 of schreibersite with dilute acid. 



Cohenite occurs in thin plates and rounded grains, none of which 

 show any evidence of crystallization. When fresh, the mineral is 

 dull tin-white in color, but soon changes to a bronze-yellow. The 

 material analyzed contained some schreibersite, as shown by the 

 phosphorus content.- Its density was 7.612 and had the following 

 percentage composition : 



Fe 91 . 290 



Ni 2 . 480 



Co 0. 100 



C 5-960 



P 0.015 



The nickel-iron alloy, taenite, occurs as very thin tin-white flexible 

 lamellae having a brilliant metallic luster. An analysis gave : 



Fe 72 . 160 



Ni 27.750 



Co o . 020 



Cu 0.000 



P 0.045 



C 0. 120 



