De Lury — Cobaltite in Northern Ontario, Canada. 275 



Akt. XXI. — Cobaltite Occur ring in Northern Ontario, 

 Canada ; by Justin S. De Lury. 



The vein containing the cobaltite described in this note is 

 situated in the southeastern part of Coleman Township, on 

 the claim owned by Mr. John Columbus, which is near the 

 recently discovered cobalt-silver mines of Northern Ontario, 

 The country rock, Huronian slate-conglomerate, contains most 

 of the valuable deposits of the district. The bulk of the vein 

 matter is quartz, which contains, besides the cobaltite, small 

 quantities of chalcopyrite and pyrite. The part of the vein 

 containing the cobaltite crystals varies from six to eight inches 

 in width. 



The mineral crystallizes in cubes and octahedra, but 

 usually in combinations of these two forms. It is of a pure 

 silvery white color, except on some weathered faces which 

 have a red tarnish. The crystals are very brittle, and when 

 broken show a rough uneven fracture. 



Owing to the brittleness of the crystals, good specimens for 

 examination can be obtained only from weathered portions of 

 the vein. Some of these crystals were carefully cleaned and 

 examined on a Goldschmidt two- circle goniometer. The cubic 

 and octahedral faces, although giving 

 sufficiently good reflections to determine 

 them as such, were much pitted and 

 striated (see fig. 1), thus giving a series 

 of reflections. Several crystals were 

 examined and of all the reflecting faces 

 only one was found which did not corre- 

 spond to the cubic or octahedral positions ; 

 it corresponded more closely to (342) 

 than to any other form. However, since 

 it was the only occurrence of this form, 

 it may be safer to assume that it is not a crystal face but a 

 contact face. 



Co 29-10 



Fe 4-55 



Ni . 0-97 



As 44-55 



S 20-73 



II. 



III. 



29-17 



35-54 



4-72 







1-68 







44-77 



45-18 



20-23 



19-28 



An analysis was made of powder obtained from carefully 

 cleaned crystals. The result of this analysis is presented in 

 column I. For purposes of comparison an analysis of cobalt- 



