58 



COLORADO FERBERITE AND THE WOLFRAMITE SERIES. 



direction of the 6 axis than the original crystal. From the sharp edge 

 on one side such cleaved pieces show a peculiar axlike shape. (See 

 fig. 11, crystal 2.) The penetration twins (figs. 17, 18, p. 64, and PL VIII, 

 A, p. 19) are generally of this habit, and the contact twins (figs. 14 

 and 15, p. 63) are of the tabular or third habit. The wedge-shaped 

 crystals of this first habit are generally poor in forms, few being 

 found except the common ones, a{100}, c{001}, Z{210}, m{110}, 



Habit 2. The short prismatic habit, somewhat flattened parallel to 

 a{100}, is the common habit for the wolframite group in general and 

 is fairly abundant on the Colorado ferberite. An example was shown 

 in figure 4 (crystal 1), and figure 12 illustrates the same combination 

 as shown in figure 4, but with a habit intermediate between the first 



or wedge shaped and the second or 

 short prismatic . The two habits show 

 all gradations, and it is impossible to 

 refer some crystals to one of these two 

 habits rather than to the other. Fig- 

 ure 12 does not illustrate any partic- 

 ular crystal measured, but many were 

 seen having about the relative pro- 

 portions shown in the figure. 



Habit 3. The tabular habit may be 

 considered as a further development 

 of the change from habit 1 to habit 

 2, which is intermediate between 

 habits 1 and 3. Single crystals of 

 this habit, as shown in figure 5, are 

 rare, but in contact twins they are 

 fairly abundant. The orthopina- 

 A, coid, a{100}-, is strongly striated in 

 the twin crystals of this habit, whereas 

 the other forms in the prism zone 

 are in general nearly free of striae. 



Habit 4. The cubic crystals were found abundantly on one specimen, 

 a side of which was literally covered with them (PI. VIII, B, p. 19, and 

 fig. 6). They were small, few being over a millimeter in length, and were 

 highly iridescent. Some of the crystals are slightly elongated in the ver- 

 tical direction, whereas others are nearly perfectly cubic. The shape of 

 the crystals is conditioned by the combination being essentially that 

 of the three pinacoids, a{100}, ft {010}, c{001}, two of which are at 

 right angles to each other, and the third very nearly so, the angle 

 being 89 32'. The dome 2(102} is always present, and the pyramid 

 A { 1 12 } is usually developed. The crystals of this habit are very poor 

 in forms. 



B 



FIGURE 8. Cleavage pieces of crystals, 

 thin tabular; S, long, prismatic. Forms: 

 c{001>, &{010> cleavage, a{100>, Z-J210}. 



