258 TERMINOLOGY. . 185. 



its own inherent powers, and does not depend upon' its 

 support, in as much as we are led to suppose both of them 

 to he of contemporaneous origin. 



Massive minerals of a smaller size are also called dissemi- 

 nated minerals, which have again been subdivided according 

 to the size of the particles. Very large masses of amor- 

 phous minerals sometimes enter into the composition of 

 rocks, as rhombohedral Lime-haloide and prismatoidal Gyp- 

 sum-haloide, several varieties of Iron-ores, &c. Under 

 these circumstances they assume the shape of beds, &c., 

 the consideration of which is no longer an object of Natu- 

 ral History. 



. 185. ACCIDENTAL IMITATIVE SHAPES. 



The accidental imitative shapes presuppose an 

 empty space, which has been filled up by the indi- 

 viduals of compound minerals, to which is trans- 

 ferred the form of the pre-existing space. 



In this case, the shape which the mineral assumes is not 

 a consequence of the properties inherent in the mineral, 

 or peculiar to its nature, but it merely belongs to that space, 

 in which the formation takes place. The sides of this space 

 serve as support for the individuals. Thus, at first a coat- 

 ing is formed, which consists of small, but in many cases 

 very perceptible crystals, whose apices are turned towards 

 the inside of the empty space. This accounts for the hol- 

 lowness of many imitative forms of this kind, of which the 

 cavities are still lined with crystals. Sometimes also we find 

 in the interior of such specimens, implanted globular, reni- 

 form or botryoidal shapes, &c., in short, imitative forms de- 

 pending upon the crystallisation of the mineral itself. Yet 

 the external shape of the whole, or of the compound mi- 

 neral, must always be considered as an accidental imitative 

 shape. 



If the whole of the space is entirely filled up, there re- 

 mains nothing else but the mode of composition of the in- 



