60 



COLORADO FERBERITE AND THE WOLFRAMITE SERIES. 



Habit 5. The rhombic crystals are very abundant on some specimens 

 and other habits are then entirely absent. (See Pis. XI and XII.) 

 The rhomboids consist of either a single crystal bounded by plane sur- 

 faces or of an agglomeration of innumerable crystals, each deviating a 

 little more from strict parallelism with the first unit. The crystals are 

 generally elongated parallel to the c axis, as shown in figure 7, though 

 some of them are more nearly equidimensional, as shown in figure 13 

 (crystal No. 24). The characteristic combination is 6(010}, a{100}, 

 2{102}, and other forms are rare. Many of these rhombic crystals are 

 fairly large, the longer diameter of ^{102} in average individuals meas- 

 uring nearly half a centimeter. 



COMBINATIONS. 



The combinations observed on the 38 crystals measured are shown 

 in the following tables, wherein the different crystals have been 

 grouped according to their habit, as the various habits have a mark- 

 edly different combination. Thus the essential forms, that is, those 

 which are characteristic for a certain habit, are given below for the five 

 different habits observed. The forms are further grouped as promi- 

 nent or not prominent, depending on whether or not they have a 

 decided influence on the shape of the crystal. Forms that are not 

 prominent are placed in parentheses. 



Characteristic forms for each crystal habit. 



Combinations on crystals with wedge-shaped habit. 



