20 COLORADO FEEBERITE AND THE WOLFRAMITE SERIES. 



The next year Rammelsberg * published an article on ferberite 

 with an analysis of his own material (see analysis No. 82) from the 

 same locality as that described by Liebe. He quotes Liebe's analysis 

 and shows that the iron oxide and tungsten trioxide are not in a 

 simple ratio and that there is an excess of iron oxide. Neither 

 mineral was pure, and the analyses are not very satisfactory, so 

 that calculation of iron in excess is uncertain, for it was probably 

 present as an impurity and not as a part of the mineral. Liebe 

 deducted 1.39 per cent limonite from his analysis. 



It seems certain that the calcium present should be calculated as 

 scheelite, for scheelite almost always if not invariably accompanies 

 otlier tungsten materials. It is not visible in all specimens to~tHe 

 unaided eye, but microscopic examination generally shows it as inter- 

 stitial, inclosed in the wolframite crystals, filling vugs, or occurring 

 separately in the deposit. (See PL V, p. 14, and PL XIII, A and B, 

 p. 30.) 



Some magnesium was found, but this element is not known to be a 

 constituent of tungsten minerals, although A. M. Finlayson 2 gives 

 an analysis of scheelite from Donaldsons, New Zealand, containing 

 0.2 per cent MgO, which. he considers to be combined with WO 3 , 

 taking the place of CaO, and Damour 3 considered that both calcium 

 and magnesium might take the place of iron or manganese in wolf- 

 ramite. That magnesium takes the place of either calcium or iron 

 m tungsten minerals seems to me altogether unlikely. If it did 

 so, some pure tungsten mineral that is, some mineral which could 

 be shown by microscopic or other examination not to contain par- 

 ticles of other substances would probably be found in which the 

 magnesium would form a considerable part of the mineral, just as 

 do those elements known to form natural tungstates namely, calcium, 

 copper, iron, lead, and manganese. Therefore, in recalculating these 

 and other analyses on pages 24-35, neither magnesium nor calcium 

 has been considered as belonging to the wolframite. 



To obtain a basis for differentiating ferberite from the remainder 

 of the wolframite group all the analyses of wolframites (by which 

 term is meant all members of the iron-manganese tungstate series) 

 available to the author have been collected for comparison. More 

 than 300 analyses were examined, but of these some represented ores 

 rather than minerals; in many the WO 3 had been determined by 

 difference, which amounts to little more than a guess; in some the 

 figures gave evidence that either the analytical work was bad or that 

 the material was so impure that no proper comparison of the results 

 would be possible. Where several analyses of the same material were 

 obtained, only one has been tabulated. 



1 Rammelsberg, C. F., tiber die chemische Zusammensetsung des Ferberite: K. Akad. Wiss. Berlin 

 Monatsber., Jahre 1864, pp. 175-176, 1865. 



2 Finlayson, A. M., The scheelite of Otago: New Zealand Inst. Trans, and Proc., vol. 40, p. 112, 1908. 



3 Damour, A., Sur le wolfram tantalifere du dSpartement de la Haute-Vienne: Soc. ge"ol. France Bull., 

 2d ser., vol. 5, p. 108, 1848. 



