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On Pseudomorphous Minerals. By Dr J. Keinhard Blum.* 



Dr Blum, in his interesting volume, divides all Pseudo- 

 morplis into two classes : — 



Class I. P.jeudomorphs produced by a partial change in 

 the composition of the original mineral. 



Class II. Pseudomorphs produced by a complete displace- 

 ment of the original mineral by another. 



In the first class, one or more elements are removed, added, 

 or introduced by substitution ; and these three modes consti- 

 tute three divisions of this class of pseudomorphs. As an 

 example of the first of these subdivisions, we instance Gay- 

 Lussite changed to calc-spar by the removal of carbonate of 

 soda and water ; the second, anhydrite, changed to gypsum 

 by the addition of Avater ; the third, gypsum changed to calc- 

 spar, by the substitution of sulphuric acid for carbonic acid. 



In the second class, to form the pseudomorph, the original 

 mineral is wholly removed and replaced by another. 



The following catalogue contains the various examples 

 enumerated by Dr Blum of these different kinds of pseudo- 

 morphs : — 



CLASS I. 

 Subdivision 1. 

 Pseudomorph. Form Imitated. 



Calc-Spax, ^ Gay-Lusslte. 



Kyanite, Andalusite. 



Steatite, Hornblende. 



Native Copper, Red Copper-Ore. 



Vitreous Silver, Red Silver-Ore. 



Subdivision 2. 



Gypsum, Anhydrite, 



Mica, Finite, 



Antimony Bloom, Native Antimony. 



Anglesite, Galena. 



Specular Iron, Magnetic Iron. 



Brown Iron-Ore, Specular Iron. 



Malachite, Red Copper-Ore. 



Variegated Co^jper-Ore, Vitreous Copper. 



Copper Pyrites, Vitreous Copper. 



* Vide the work entitled, " Die Pseudomorphosen des Mineral- 

 reiches," by Dr J. R. Blum. 8vo, pp. 378. Stutgard. 1843. 

 VOL. XXXIX. NO. LXXVIII, — OCTOBER 1845. Q 



