. 172. OF THE STRUCTURE OF MINERALS. 233 



turc, is to make its irregular structure appear, by 

 a mechanical separation of its particles. 



Every individual, cleavable or not, may be broken. Ir- 

 regular structure, that is to say, fracture, may be much 

 more generally observed than cleavage. Fracture, how- 

 ever, on account of the want of regularity essential to it, 

 can only be of very limited use in the Natural History of 

 the Mineral Kingdom. It may here be useful, from this ob- 

 servation, to derive the important consequence, that it is 

 not a generality or a variety, but only a regularity and con- 

 stancy in the differences occurring in a natural-historical proper- 

 ty, tcJtich renders it applicable, and determines its value as a dis- 

 tinctive character in Natural History. 



Fracture is considered here as a property of individuals, 

 or of simple minerals in general, agreeably to the principles 

 of Natural History. The greater part of the varieties of 

 fracture, quoted in books on Mineralogy, on that account 

 must here be excluded, because they refer to compound 

 minerals, which in fact also may be broken in pieces. 

 These, however, will be considered in another more conve- 

 nient place. 



. 172. FACES OF FRACTURE. 



The faces in which the particles of the individuals 

 separate when broken, are termed Faces of Frac- 

 ture. 



The kinds of fracture are determined according to the 

 quality of its faces. The irregularities of these faces are 

 either round or angular. The first sometimes represent the 

 aspect of the inside of a shell. That kind of fracture which 

 is formed by such faces, is termed the Conchoidal fracture, 

 and provided with peculiar adjectives referring to the size, 

 concavity, lustre, &c. ; all this, however, without any useful 

 consequences. The angular irregularities cannot be com- 

 pared to any thing at all. The kind of fracture formed by 



