MINERA L TRA NSFORMA TIONS. 275 



majority, of the known pseudomorphs have originated in 

 this way. 



But there are others which can only have been produced 

 by the gradual alteration of one mineral into another. It 

 may be, for example, that a crystal is found having the 

 characteristic form of Garnet, which consists at one end of 

 unaltered garnet substance, while at the other it has been 

 wholly converted into Epidote. Such a pseudomorph pos- 

 sesses the greatest interest ; it not only raises the inquiry 

 what radicles have been removed, what radicles have been in- 

 troduced during the change, and by what agencies the trans- 

 formation has been effected ; but further it cannot fail to 

 provoke some theory of the composition both of the initial 

 and final compounds. 



The complication of pseudomorphous products is not so 

 great as might be expected. That among the varied con- 

 ditions under which they have originated the total number 

 of known minerals should be so small is always surprising ; 

 but that the apparently obscure products and mixtures into 

 which they decompose prove on careful study to be identical 

 with one or other of these well-established compounds is 

 perhaps still more remarkable. Much of the material of 

 pseudomorphs was formerly referred dubiously to mixtures 

 of certain ill-defined species — clays and other hydrated sili- 

 cates for example; it was scarcely possible to determine their 

 nature by analysis, for it was uncertain how many different 

 minerals they contained. 



But since the introduction of microscopical methods 

 there is no longer any excuse for such an evasion ; the 

 optical characters of the transparent minerals have mostly 

 been determined, and it is possible to identify them in the 

 minutest crystals. 



The use of the microscope has consequently corrected 

 many mistakes which were made by the early mineralogists 

 in their determinations of pseudomorphous materials, and 

 has revealed many new transformations. 



Although recent study has done much to clear up the 

 doubts which formerly prevailed regarding the nature of 

 the resulting mineral, it cannot be said that there is the 



