Mineral Evolution. 107 



definite crystalline figure. There are, however, some 

 extraordinary exceptions. For instance, calcspar 

 comprises several hundred diverse crystals ; while 

 fluorite, pyrite, and baryte each number over a hun- 

 dred. Such diversity in the same substance is prob- 

 ably due to differing conditions during solidification, 

 although infinitesimal adulterations probably conduce 

 more to this effect. Still, behind all structural eccen- 

 tricity, the important fact remains that no matter 

 what figure a mineral may " sportingly" assume, the 

 " rogues " — as gardeners would say — are all reducible 

 to a parent type. 



The deduction consequently is, that every simple 

 or compound mineral originates from a bottom form 

 or crystal, as already alleged. For example, gold 

 crystallises as an octahedron, and as an element must 

 be built up solely of atoms of gold. Hence, if we 

 split up this octahedron into smaller pieces (a difficult 

 operation with gold, but easy enough with other sub- 

 stances, such as sugar, salt, etc.), each sub-division 

 would also be octahedric, until, after continuing the 

 process by imagination to the smallest particle of 

 gold, we finally resolve the atom, of gold itself into an 

 octahedron. The visible nugget thus accurately re- 

 presents the invisible and ultimate atomic form. 



If this deduction be correct, each element has a 

 special geometrical type-form ; thus practically estab- 

 lishing (according to the number of known elements) 

 no fewer than seventy parent types as the bottom 

 constituents of crystalline design. Below this number 



