253 TERMINOLOGY. . 183. 



from each other, those imitative shapes result, which are 

 not unfrequently met with in the above mentioned species. 



Sometimes several rows of individuals thus composed 

 join within one and the same plane in certain constant di- 

 rections, so that the individuals of the one of these series 

 do not join with those of the other, but remain separate. 

 Thus the dendritic shapes are produced, of which most dis- 

 tinct varieties occur in hexahedral Silver and hexahedral 

 Gold. The same minerals evidently shew the formation 

 of the dendritic, as also that of the dentiform, filiform, 

 and capillary shapes, in those varieties where the indivi- 

 duals constituting them still may be distinguished in the 

 compositions. To this division belong also some of the 

 superficial dendritic shapes formed in fissures. 



If the rows of individuals, thus arranged, approach so 

 near each other that they at last meet, so as to form a con- 

 tinuous mass, they are said to occur in the external shape 

 of leaves or membranes, which are among The most common 

 shapes found in hexahedral Gold, where they exhibit va- 

 rious modifications. In some of them we may still discern 

 the individuals ; in others there are striae in certain direc- 

 tions, indicating their composition, so that their mode of 

 formation does not remain doubtful. From external shapes 

 of this description, we may infer that those likewise whose 

 smooth surfaces no longer present any traces of composi- 

 tion, are yet owing to the aggregation of several indi- 

 viduals. 



Compound minerals, like those now described, may 

 again join in a new composition, in which consequently the 

 individuals are arranged in the direction of different planes ; 

 in most cases at right angles to each other. Thus the re- 

 ticulated shapes arise, of which the most distinct specimens 

 occur in octahedral Cobalt-pyrites. In these very often 

 the composition itself is still observable. Some of the re- 

 ticulated forms, however, allow of a different explanation, 

 if, instead of rows of individuals, they consist of capillary 

 crystals, like those of peritomous Titanium-ore. 



The third division comprehends the stalactit'tc and coralloidal 



