The Ottawa Naturalist. 



Vol. IX. OTTAWA, JANUARY, 1896. No. 10. 



ERYTHRITE; STILPNOMELANE var. CHALCODITE; CRYS- 

 TALLIZED MONAZITE; AND PLEOCHROIC APATITE 

 FROM SOME CANADIAN LOCALITIES. 



By W. F. Ferrier, B.A.Sc, F.G.S., Geological Survey of Canada. 

 (Communicated by permission of the Director.) 



Erythrite. 



This mineral was detected by the writer in some rock specimens 

 collected in 1893 by Mr. A. E. Barlow of the Geological Survey on the 

 west shore of Rabbit Lake, District of Nipissing, Ont. It occurs in 

 thin earthy crusts, of a dullish peach-red color, lining fissures in a 

 diabase which cuts the Huronian rocks of the locality, and is accom- 

 panied by a green mineral, apparently containing nickel and arsenic, 

 which may be the hydrous arsenate of nickel, annabergite, but the 

 available material was not sufficient for a satisfactory determination of 

 its true character to be made. 



In composition erythrite is a hydrous arsenate of cobalt contain- 

 ing when pure 38 .4% arsenic acid, 37.6 % oxide ot cobalt, and 24 % of 

 water, but the cobalt is nearly always replaced in part by nickel, iron, 

 and calcium. 



When abundant it is a valuable ore of cobalt, and its occurrence in 

 Canada has been so seldom noticed* that it was thought desirable to 

 place on record this new locality discovered by Mr. Barlow. 



As the mineral almost invariably accompanies other ores of cobalt 

 (sulphides etc.), from whose alteration it is frequently derived, a further 

 examination of the locality is to be wished for, which, even if it did not 

 reveal the mineral in workable quantity, as from its mode of occurrence is 

 scarcely to be expected, might bring to light other compounds of cobalt 

 and nickel of interest to the mineralogist. 



* It occurs in thin coatings at Prince's Mine, Lake Superior, Ont., and in some 

 quantity at a new locality discovered by the writer and described by him in the forth- 

 coming Summary Report of the Geol. Survey of Canada. 



D A D V 



