[GRAHAM] YUKONITE 21 



angles are not identical with those of normal scorodite. Kobalt-scorodite 

 is reported by Lippmann as occurring at Schneeberg in bluish crystals 

 which were not analysed (Dana, 6th Ed. p. 822). A borax bead test 

 seemed to confirm the presence of cobalt in the crystals from Cobalt; 

 but owing to the small amount of material used, and bearing in mind 

 the fact that the associated minerals are all highly cobaltiferous, the 

 result is considered doubtful. 



The specific gravity was found to be 3 '235, using methylene iodide 

 and the Westphal balance. 



The prism angle being nearly 60°, a rough measurement of the re- 

 fractive index by the M.D. method was made, and gave a mean index 

 of 1-76, with strong dispersion. There are apparently no published 

 determinations of the refractive index of scorodite with which to com- 

 pare this result. 



The writer is indebted to Mr. J. B. Tyrrell for supplying the material 

 described in the above note. 



Note. — Since the above was written, Mr. Tyrrell has obtained some additional 

 material from Cobalt, and the writer hopes to be able shortly to publish a fuller 

 description of the brown amorphous substance described here. 



Mineralogical Laboratory, 

 McGill University, 

 Montreal. 



