THE MINERALS OP IDAHO 

 Measurements of cobaltite from Brooklyn claim 



133 



A specimen collected by Frank L. Hess from the Ludwig and 

 Bascom Latest Out claim on the west fork of Blackbird Creek 

 has abundant small crystals of cobaltite, seldom reaching 1 mm. 

 in diameter, disseminated in streaks in granular quartz containing 

 some schist inclusions (pi. 2, upper). These crystals are easily 

 isolated from the matrix and are found to be cuboctahedrons as 

 shown in Figures 11 and 12. The measurements which identify the 

 forms are, in detail, as follows: 



Measurements of cobaltite from Latest Out claim 



This mineral has well-defined cubic cleavage. It behaves like the 

 preceding when heated in the closed tube or on charcoal. A sample 

 separated by heavy solutions from this sample was partially ana- 

 lyzed. It contains 20.08 per cent of sulphur and 2.18 per cent of 

 iron. No trace of nickel could be detected. A specimen from the 

 Wiley J. Rose property 1 mile north of the old camp of Blackbird 

 contains a solid vein of granular cobaltite partly altered to erythrite 

 in a quartzose schist and another specimen from the same vicinity 

 has granular crystalline streaks of cobaltite in schistose quartz making 

 up half the bulk of the specimen. This cobaltite was analyzed, 

 yielding the following results: 



Analysis of cobaltite, Lemhi County 

 Constituent Per cent. 



Cobalt (Co) 32. 38 



Iron (Fe) 4. 33 



Nickel (Ni) . None. 



Arsenic (As) 44. 07 



Sulphur (S) 18. 10 



Total 98. 88 



