102 TERMINOLOGY. 



these minerals to be compound, even though the component individ- 

 uals should no longer be perceptible. 



. 85. STRUCTURE or COMPOUND MINERALS. 



That kind of fracture which has been considered as be- 

 longing to simple minerals, does not occur in compound 

 minerals. In breaking these last, however, we produce 

 what has been called their Fracture ; and the particles of 

 the mineral separate in the Faces of Fracture. 



If the particles are still distinguishable as individuals, they must 

 be considered according to their respective regular or irregular 

 structure, to their faces of composition, and to every other character 

 which they present to the observer ; in short, they must be consid- 

 ered as simple minerals. In the present place, therefore, only those 

 compound minerals will be treated of, in which on account of their 

 minuteness, the individuals are no longer distinguishable. In these, 

 the following kinds of fracture have been distinguished. 



1. The Conchoidal Fracture, together with its various modifica- 

 tions, which depend upon size, perfection, relative depression, &c. 

 (.69.) 



2. The Uneven Fracture, which has been subdivided according 

 to the size of the asperities, into coarse-grained, small-grained, and 

 fine-grained uneven fracture. 



8. The JEven Fracture, which arises, if the elevations and de- 

 pressions upon the face of separation nearly approach to evenness. 

 These even parts of the fracture must not be confounded with faces 

 of cleavage, because they do not keep a constant direction, and are 

 only observable in compound minerals. This variety of fracture is 

 not common. 



4. The Splintery Fracture, which is produced, if upon the face 

 of separation, detached scaly particles remain, joined to the mass 

 by their thicker end. These particles are rendered visible by that 

 portion of light which passes through them; and the splintery frac- 

 ture, therefore, does not occur in perfectly opaque minerals. It 

 may occur at the same time with the conchoidal, or another kind of 

 fracture. 



5. The Hackly Fracture has been sufficiently explained in . 69. 



