M IN ERA L TRA NSFORMA TIONS. 283 



this difficult problem ; they may excite the derision of or- 

 ganic chemists ; but so long as the methods available in 

 organic chemistry have no application in mineralogy, and 

 until other means of exploring the constitution of even the 

 simpler silicates are discovered, we have to make the most 

 of the means at our disposal. 



It will be observed that Serpentine and Kaolin have a 

 precisely similar composition, three atoms of magnesium in 

 the one being replaced by two atoms of aluminium in the 

 other. Such common decomposition products deserve 

 special study, since they undoubtedly represent simple sub- 

 stances of an extremely stable nature into which the less 

 stable silicates of the igneous rocks tend to degenerate 

 under ordinary conditions ; no mineral is more stable than 

 Talc ; articles made of Steatite (a compact Talc), though it 

 is so soft a material, have withstood the wear and tear of 

 centuries far more successfully than most materials worked 

 by man ; it is difficult to believe that such minerals do not 

 possess a very simple constitution. 



For this reason also we might expect them to present 

 some similarity not only among themselves, but also to those 

 anhydrous minerals (pyroxenes, amphiboles, felspars) of 

 which they are the hydrated representatives. It is, how- 

 ever, certain that before these relationships can be success- 

 fully traced, the natural pseudomorphs need most careful 

 and detailed study in order that their initial and final states, 

 and also the intermediate stages through which they pass, 

 may be definitely established. 



H. A. Miers. 



