90 Mr HAIDINGER on the Parasitic Formation 



formula 2 Fe + 3 Aq, and which contains 14.7 per cent of wa- 

 ter. One atom of the carbon contained in the original com- 

 pound will therefore go away in the state of carbonic acid, while 

 the other must be transformed into oxide of carbon, in order to 

 convert the protoxide of iron into a peroxide. The change in 

 those masses has taken place so insensibly, that the action of 

 the power of crystallization was prevented, and the interior pre- 

 sents a pretty uniform texture ; but, at the same time, some par- 

 ticles of the hydrate of iron commonly also follow their own innate 

 attraction, and form geodes of brown hematite, that is, of prisma- 

 tic iron-ore. Hiittenberg in Carinthia has perhaps no equal in 

 illustrating the exactness of this explanation, for the distinct- 

 ness of the specimens which it affords. The geodes occurring at 

 that place, of various sizes, are very frequently adorned with 

 crystals of arragonite, of calcareous spar, of prismatic manganese- 

 ore, or with the silvery flakes of another manganesian mineral, 

 whose exact chemical composition has not yet been ascertained. 

 With the decomposition of the sparry iron is also intimately con- 

 nected the formation of those beautiful coralloidal varieties of 

 arragonite known by the name of flos ferri, which are found in 

 caverns near the surface of the rocks, as at Eisenerz in Stiria. 



The ankerite, or paratomous lime-haloide of MOHS, is al- 

 so apt to be decomposed in a similar manner. But as it is a 

 compound of the carbonates of lime and iron, in which the for- 

 mer amounts to more than half the weight, only what might be 

 termed a skeleton of the hydrate of iron remains, while the rest 

 of the ingredients disappear by the action of chemical agents. 

 The texture of the remaining mass is much less compact than 

 that of the residue left by the decomposition of the sparry iron. 



The product of the decomposition of the two species last 

 mentioned, is exactly the same as the substance which remains, 

 when iron-pyrites suffers a decomposition, without changing its 

 form. Both species, the hexahedral and the prismatic iron-py- 



