134 RE-EXAMINATION OF AMERICAN MINERALS. 



Our attention was first called to this mineral from the 

 unusual relation of the sulphur to the metals in its composition, 

 it being, we believe, the first example of a natural subsulphuret 

 that had been observed, the relation being E* S 3 . 



Having been furnished, through the kindness of Prof. Dana, 

 with an abundance of the mineral to select from, which he had 

 procured from original specimens in the hands of Prof. Booth, 

 it was carefully separated from the copper pyrites with which 

 it is associated. A re-examination of it gives the following for 

 its physical and chemical characters: Hardness 5.5; sp. grav. 

 4.85 ; * luster metallic ; color steel - gray ; fracture uneven, 

 without sufficient indication to make out clearly the nature 

 of its cleavage. The results of three analyses are 



12 3 



Sulphur 41.93 40.94 40.99 



Cobalt 37.25 38.21 37.65 



Copper 17.48 17.79 19.18 



Nickelt 1.54 1.54 1.54 



Iron 1.26 1.55 1.40 



Arsenic trace trace trace 



99.46 100.03 100.76 



These correspond to the general formula ES + E 2 S 3 , as will 

 be seen by comparing the amount of sulphur required for the 

 metals indicated in the three analyses with the quantities found. 



1 Sulph. 2 Sulph. 3 Sulph. 



Cobalt 37.25 27.00 38.21 27.68 37.65 27.21 



Copper 17.48 11.65 17.79 11.88 19.18 12.78 



Nickel 1.54 1.12 1.54 1.12 1.54 1.12 



Iron 1.26 .93 1.55 1.15 1.40 1.03 



40.70 41.83 42.14 



Substituting cobalt for the copper, iron, and nickel, the entire 

 amount of the cobalt would be represented in the three an- 

 alyses by 56.37, 57.92, and 58.50 per ct. The formula requires 



Atoms. Pr. ct. 



Sulphur 4 42.06 



Cobalt 3 57.94 



This is the formula and constitution of linnseite, and the min- 

 eral in question is a copper linnseite similar in composition to 

 the one from Eiddarhythan, Sweden. 



- : - It may be well to remark that there is a typographical error in the 

 statement of the sp. grav. of linnseite in Dana's Mineralogy; it is never 

 above 5.00. 



t Only one estimate of nickel made. 



