176 



Decomposition of Iron Pyrites 



obtained, by means of a magnet, among the ernshed powder. The 

 material selected for the specific gravity determination was 

 fonnd, under a low power of the microscope, in reflected light, 

 to consist of an intimate intermixture of the shining grayish 

 white marcasite and white quartz ; the lowering of the specific 

 gravity to that of pyrrhotite appears therefore to be merely due 

 to this accidental ingredient. Decomposition : a bronze-yellow 

 to ^brownish black tarnish on the surface of most crystals, and a 

 minute efflorescence of white vitriol within the mass. 



MARCASITE. 







d 





Supposed 









iO 



^ 



Constitution. 









o * 



S c« 







Tendency 



No. 



Locality. 





n 



w'^ 



o 





^ 



< 



|o 



OQ 





TO 







5 



4.987 



2^ 



5.032 



|0 



gcrJ 



Decomposition. 



1 



Cumberland, Eng. 



10.55 



89.45 



Slight tarnish. 



2 



Canterbury, Eng. 



4.949 



4.077 



28.17 



71.83 



" 



3 



Nova Scotia. 



4.943 



3.341 



30.99 



69.01 



" 



4 



Bohemia. 



4.942 



1.363 



31.45 



68.55 



»' 



5 



Folkestone, Eng. 



4.935 



4.377 



34.74 



65.26 



" 



6 



Belgium. 



4.915 



3.701 



44.18 



55.82 



Slight tarnish and vit- 

 riolescence. 



7 



Hannover. Germ'y. 



4.909 



1.944 



47.03 



52.97 



Slight tarnish. 



8 



Marsden'sDi^gings, 

 Galena. 111. 



4.903 



3.486 



49.89 



50.11 



Slight tarnish and vit- 

 riolescence. 



9 



Galena. 111. 



4.895 



5.050 



53.73 



46.27 



Slight tarnish. 



10 



Champion, N. Y. 



4.888 



5 018 



57.08 



42.92 



Tarnish and ochreous 

 film. 



11 



Folkestone, Eng. 



4.887' 



2.445 



57.56 



42.44 



Tarnish and ochreous 

 film. 



12 



Joplin. Mo. 



4.885 



2.614 



58.51 



41.49 



Tarnish. 



13 



New York, N. Y. 



4.882 



3 762 



59.93 



40.07 



Tarnish and ochreous 

 film. 



14 



Dover, Eng. 



4 881 





60.41 



39.59 



Slight tarnish. 



15 



Canada. 



4.872 



1.445 



64.76 



35.24. 



Tarnish and ochreous 

 film. 



16 



Galena, 111. 



4.868 



1.708 



66.69 



33.31 



Tarnish. 



17 





4.867 



2.484 



67.17 



32.83 



'• 



20 



" 



4.863 



2.069 



69.10 



30.90 



" 



21 



Littmitz. Bohemia. 



4.859 



3.618 



71.05 



28.95 



" 



22 



Joplin, Mo. 



4.858 



3 628 



71.53 



28.47 



" 



24 



Galena, 111. 



4.827 



2.193 



86.65 



13 35 



Tarnish and vitriol- 

 escence. 



25 



'• 



4.812 



2.239 



94.07 



5 93 



Tarnish. 



