SECTION VII. 

 PRIMARY FORMS. 



THE derivative or parent form, from which the 

 secondary forms of any crystallized mineral may be 

 conceived to be derived by the operation of certain 

 laws of decrement, has been denominated the primary 

 form of such mineral. 



It may be added that the primary form of a mineral 

 should not be inconsistent with its known cleavages, and 

 it should generally be such also as would produce the 

 secondary forms of the species to which it belongs by 

 thefezvest and simplest laws of decrement.* 



It is for the sake of rendering our notions of a 

 primary form more precise, that we give this limiting, 

 and in some degree arbitrary, definition of the term. 

 Our purpose throughout this treatise is, to find the 

 shortest and most direct road from the secondary 

 crystal to the mineral species to which it belongs. 



But as we must travel first from the secondary to 

 the primary form, it is essential that our ideas of that 

 figure which we agree to call the primary form, should 

 be as precise as possible. 



The primary forms of crystals may sometimes be 

 developed by cleavage. 



* The term primary, so defined, is merely relative, being used in con- 

 tradistinction to secondary. It appears therefore preferable to the term 

 primitive, which has been generally used to designate this original or 

 parent form, and which seems to imply something more intrinsic, and 

 absolute, than is required by the science into which it is introduced. 



