23!< TERMINOLOGY. . 173. 



these asperities, has received the denomination of the Vn. 

 even fracture, and has been divided again according to dif- 

 ferences in the size of its grain, but this too is of very 

 little value. There exists an immediate transition be- 

 tween the two kinds of fracture, in which only arbitrary 

 limits can be fixed. The other kinds of fracture, the even 

 fracture, the fibrous fracture, the splintery fracture, either 

 do not refer to simple minerals, or they do not belong to 

 structure at all. The hackly fracture is not produced by 

 breaking, but by tearing a mineral in pieces. Foliated 

 fracture is cleavage ; the passage of the folia means the same as 

 the directions of cleavage ; regular fragments are the forms 

 of cleavage ; and the varieties of radiated fracture are the 

 same, only referring to compound minerals. 



. 173. CHARACTER OF FRACTURE. 



The faces of fracture preserve no constant direc- 

 tion. In this particular, fracture is essentially dif- 

 ferent from cleavage. 



Individuals without cleavage, or with a very indistinct 

 cleavage, or such individuals whose particles possess only a 

 small degree of coherence, may be broken in any direction, 

 that is to say, no direction could be indicated beforehand, 

 and determined in reference to the situation of any line or 

 plane, in or parallel to which the mineral would break. 

 Fracture, therefore, has no constant or determined direction ; 

 neither can it be continued according to parallel planes, al- 

 though, by a continual diminution in size, we may carry on 

 the separation of the particles to an indefinite extent. 



The same applies also to those individuals which allow of 

 cleavage, if they be broken, that is to say, if their particles 

 be separated in any other directions than those of cleavage. 



The irregular structure is very often observable, along 

 with the regular structure in the same individuals. 



