DEFINITION OF FERBERITE AND OTHER MEMBERS OP THE SERIES. 37 



Tantalum and columbium are common in wolframites and their 

 commercial possibilities have been investigated rather extensively. 1 

 Mennicke mentions 1.5 per cent as the highest content of the oxides 

 known in wolframites, but the ferberite from Cave Creek, Ariz., 

 carries 2.2 per cent of the combined TajO 6 and Cb a O 8; according to 

 Wherry's analysis. The form in which these oxides are present is 

 not positively known, but it seems probable that, as suggested by 

 Damour, 2 they occur as minute particles of columbite. In the 

 ferberite of Cave Creek irregularities in cleavage faces seem to be due to 

 the presence of small bodies of a different black opaque mineral which 

 may be columbite. I hope to do further work upon this subject. 



DEFINITION OF FERBERITE AND OTHER MEMBERS OF 

 THE WOLFRAMITE SERIES. 



The continuity of the wolframite series as indicated by the analyses 

 quoted shows that its customary division into hubnerite, wolframite, 

 and ferberite must of necessity be arbitrary. The analysis on which 

 the species ferberite is based (No. 79) gives a content of 3.02 per cent 

 MnO, equivalent to 3.7 per cent MnO or 15.7 per cent MnWO 4 after 

 recalculation. Great accuracy can not be claimed for the figures 

 showing the constituent molecules, as the material was impure. In 

 defining the species it can hardly be held that 3.07 per cent MnO or 

 15.7 per cent MnWO 4 must mark the extreme limit of Mn allowable in 

 ferberite. As by common usage the wolframite series is divided into 

 three groups, 20 per cent MnWO 4 seems to be a convenient and 

 reasonable limit to place upon the MnWO 4 allowable in a ferberite, and 

 convenience would seem to indicate for hubnerite a similar limit of 20 

 per cent for its content of iron tungstate, FeWO 4 . For the mixtures 

 between these end members the older term wolframite may properly 

 be retained, and this term may well serve also as a general or field name 

 for the members of the series which can not be definitely identified. 



I therefore propose the following definitions for the members of the 

 wolframite series: 



Ferberite : A monoclinic iron tungstate having when pure the com- 

 position FeWO 4 . It may contain not more than 20 per cent of the 

 hubnerite molecule, MnWO 4 . 



Hubnerite : A monoclinic manganese tungstate having when pure 

 the composition MnW0 4 . It may contain not more than 20 per 

 cent of the ferberite molecule, FeWO 4 . 



' Mennicke, Hans, Die Metallurgie des Wolframs, pp. 125-130, 1911. 



* Damour, A., Sur le wolfram tantalifere du d^partement de la* Haute-Vienne: Soc. g<k>l. France Bull., 

 2d ser., p. 108, 1848. 



