100 . TERMINOLOGY. 



. 83. SINGLE AND MULTIPLE COMPOSITION. 



The single composition takes place, if a compound min- 

 eral consists of individuals ; but if the particles of compo- 

 sition are again composed, then the composition is multiple. 



The compositions, treated of in the preceding articles, are single 

 compositions. 



But there exist particles of composition, which are again compo- 

 sed of granular particles, which last only, are real individuals. 

 They join into those masses which again, on a larger scale, produce 

 a granular composition. Thus, in Dolomite we sometimes have 

 granular particles, consisting of columnar particles ; and in Carbo- 

 nate of Lime and in Chalcedony, columnar particles are observed 

 consisting again of columnar individuals. 



. 84. CHARACTERISTIC MARKS OF COMPOSITION. 



Imitative shapes, and the want of cleavage, are the chief 

 characters, from the presence of which composition may be 

 inferred, if this should not be observable at first sight. 



An individual formed under such circumstances as lie beyond 

 the reach of foreign influence, will always assume a regular form. 

 If, therefore, we meet with minerals which evidently have not been 

 acted upon by any such circumstances, and which nevertheless do 

 not present any regular form, we may infer, with perfect security, 

 that the mineral is not a simple one, but that it is a compound of 

 several individuals. 



With regard to the accidental imitative shapes, it is evident, that 

 not even those which are regular can be the forms of simple miner- 

 als, because they are altogether accidental ; whereas the forms of 

 simple minerals are founded in the nature of the individuals them- 

 selves. Hence the imitative shapes, of whatever kind they may be, 

 are, in every instance, infallible characters from which the compo- 

 sition of the minerals may be inferred. But we could suppose that 

 a compound mineral might consist of particles in a perfectly paral- 

 lel position, but so small that the composition can no longer be ob- 

 served, so that the directions of cleavage of the single particles, o,r 

 supposed individuals in, one of them are the continuation of those ift 



