Noie on the Occurrence of Scorodite, etc., at Cobalt, Northern Ontario, 



Canada. 



By R. P. D. Graham. 



A substance which resembles yiikcnite very closely in general 

 appearance has recently been found by Mr. J. B. Tyrrell at Cobalt, 

 Northern Ontario (Vein 49 of the Nipissing Mine). 



This material has a coffee-brown colour, paler than yukonite, and 

 is occasionally banded in difl'erent shades; like yukonite, also, it is 

 amorphous, breaking with a conchoidal fracture, and the lustre is \itre- 

 ous to resinous. H = 3 - 4; Sp. G. = 2.83. 



Together with a paler yellow ochreous substance, it encrusts mas- 

 sive nickeliferous smaltite (or chloanthite), and there are also associated 

 with it erythrite and on one of the specimens, a few minute crystals 

 of scorodite. The erythrite, in the form of small botryoidal masses 

 composed of radiated needles, is often seen forming a coating over the 

 amorphous brown substance, and has probably been derived from its 

 alteration. 



The association with erythrite is interesting in view of the fact that 

 yukonite is accompanied by symplesite (which is isomorphous with 

 erythrite, containing iron in place of cobalt); and it was thought pos- 

 sible that the substance from Cobalt might be a Co-Ni compound an- 

 alagous to yukonite, since the two materials are so much alike physi- 

 cally, and give rise to such nearly related decomposition products. 



A preliminary examination showed that it is easily soluble in 

 hydrochloric acid, and that it contains As, Fe, Co and Ni, but no Ca; 

 there was no reaction for a sulphate or phosphate. When heated in a 

 small blowpipe flame, it is easily fusible to a strongly magnetic mass, 

 and in the closed tul:)e it yields much acid water and a w4iite de})osit of 

 arsenious oxide, the reaction taking place more readily when the sub- 

 stance has been previously mixed with charcoal powder. 



In the analysis, the arsenic was precipitated as tri-sulphide from 

 the reduced solution, dissolved and converted to magnesium pyro- 

 arsenate. The cobalt and nickel, after removal of the iron, were de- 

 posited electrolytically from an ammoniacal solution of their sulphates, 

 and after the deposit had been weighed and dissolved, the cobalt was 

 separated by precipitation with potassium nitrite, and both it and the 

 nickel were then determined l^y precipitation with potash and bromine 

 water. Owing to the small amount of material available, only one 



