VI. On the Parasitic Formation of Mineral Species, depending 

 upon Gradual Changes, which lake place in the Interior of 

 Minerals, while their External Form remains the same. 

 By WILLIAM HAIDINGER, ESQ. F. R. S. EDIN. 



(Read IQth March 1827. ) 



mineralogist is conversant with some of the facts rela- 

 tive to the subject of this paper. Some of the observations enu- 

 merated, are comparatively new, as the attention of naturalists 

 has been only of late more particularly directed towards these 

 facts. Others, which I have had an opportunity of collecting 

 myself, I trust will not be considered uninteresting, as they tend 

 materially to rectify certain ideas connected with the determi- 

 nation of the mineralogical species, the most important branch 

 of natural-historical research. 



The mutual attraction of the elements of mineral bodies, can- 

 not at present enter into play on so extensive a scale, as during 

 the period of the formation of those enormous masses of rocks, 

 particularly those having a crystalline character, which form a 

 great portion of our globe ; for these bodies are the result of the 

 very action of the elements on each other, by which they have 

 arrived at a settled state. There are some agents, however, 

 which we every day observe to affect, more or less considerably, 

 the constitution of certain minerals, more prone than others to 

 decomposition. Many species of the class of salts are continu- 

 ally destroyed by their solution in water, and regenerated by its 

 evaporation. Iron-pyrites, exposed to the alternating influence 

 of water, the oxygen of the atmosphere, and the changes of tem- 

 perature produced in the natural course of the seasons, or by the 



VOL. XI. PART I. K 



