266 



MINERALOGY 



Acicular is where the prismatic habit is so accentuated that the 

 crystals are long and needle-like, as stibnite or rutile. 



FIG. 378. Tabular Barite and Acicular Stibnite. Felsobanya, Hungary. 



When still more attenuated or hairlike, they are said to be 

 capillary, as millerite, Fig. 379. 



Fibrous is when the fine hairlike crystals are parallel in arrange- 

 ment, and usually 

 easily separable, as 

 asbestos, Fig. 380. 



All the above habits 

 may be illustrated by 

 specimens of the same 

 mineral species. 



The surfaces of 

 crystal faces and 

 mineral aggregates 

 differ in appearance 

 and the following de- 

 scriptive terms are in 

 use : 



Striated. Crystal faces are often crossed by striations, which 

 are always parallel to some definite crystallographic direction and 



FIG. 379. Millerite, Antwerp, Jefferson County, 

 New York. 



