CRYSTALLOGRAPHY OF FERBERITE FROM COLORADO. 



By WALDEMAR T. SCHALLER. 



PREVIOUS PUBLICATIONS. 



The several papers mentioned by Mr. Hess in his part of this report 

 give some general facts in regard to the habit and size of crystals of 

 ferberite. Two other papers, by Warren and by Moses (see Bibliog- 

 raphy, pp. 74-75), give descriptions of ferberite crystals which may 

 have come from this locality. The crystal figured by Warren is said 

 to have come from South Dakota, though he states that the exact 

 locality could not be ascertained. From the appearance of the crystal 

 it is more likely to have come from Colorado than from South Dakota. 

 The crystal figured and described by Moses as crystallized wolframite 

 from Boulder County, Colo., is very similar to those here described. 



These two papers are the only publications on the crystallography 

 of the ferberite from Colorado that could be found. 



GENERAL CHARACTER OF THE CRYSTALS. 



MODE OF OCCURRENCE. 



In the specimens examined the ferberite crystals are perched on 

 the country rock in groups or they line or nearly fill the cavities or 

 fissures in the matrix. Layers of ferberite several centimeters thick, 

 consisting of crystals whose bases have coalesced, are found on the 

 rock. Much of the ferberite, which at first glance seems to be mas- 

 sive, is found on closer inspection to be a granular compact mass of 

 small crystals. 



The crystals occur isolated as distinct individuals (Pis. VII, p. 18, 

 and VIII, p. 19), in groups of parallel or nearly parallel individuals 

 (Pis. IX, p. 20, and X, p. 21), or in confused masses consisting of 

 numerous abutting and even penetrating crystals. Twins are com- 

 mon, though single untwinned crystals are far more plentiful. The 

 nearly parallel groupings are of two kinds: (1) A group of flattened 

 crystals which may depart several degrees from strict parallelism and 

 which are joined by the a(100) faces (fig. 1); and (2) crystals joined 

 by the c(001) faces and superposed, the line of demarcation of the 

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