588 VEINSTONES. 



or metallic, and under every possible modifica- 

 tion of form and mixture. The knowledge of 

 these which the student of rocks is presumed to 

 possess, will enable him to determine the nature 

 of such mixtures ; while their real nature may 

 generally be decided, by their containing those 

 mineral substances, whether earthy or metallic, 

 which are known not to enter as constituents into 

 beds of rock. 



To attempt a complete catalogue of such vein- 

 stones, would be to make a tedious enumeration 

 of possibilities ; as they are necessarily infinitely 

 varied, and cannot well be connected by any gene- 

 ral rules. It will be sufficient to remark, that the 

 fragments which they contain may vary infinitely 

 in size, disposition, and mixture, and that they 

 must necessarily consist, in some place or other, 

 of every rock in which veins pre known to exist. 

 The cementing ingredient must also be as various 

 as are the minerals that occur in veins. But it 

 may be remarked, that veinstones are generally 

 to be distinguished from all other mechanical 

 mixtures of rock, by the existence of occasional 

 vacuities among the fragments, or of crystals, or, 



