306 Mr Haidinger's Description of ' Pyrolusite, 



Pyrolusite was found by M. Gmelin to be a superoxide of 

 manganese. In most mineralogical works, the descriptions 

 given of the only species that they contain, is made up of the 

 forms and colour of manganite ; and the hardness, streak, and 

 colour of pyrolusite. 



This is at once the most common species, and the most use- 

 ful one, on account of the large quantity of oxygen which it 

 contains. It is the ore of manganese properly so called, in an 

 economical point of view, and has been extensively, though not 

 exclusively, worked for in many countries. The principal mines 

 are the ancient ones of Ilmenau, Friedricksroda, Reinwege, 

 Elgersburg, and other places in Thuringia. Almost every 

 one of the varieties, particularly the compound ones, granular 

 and columnar, are found there, consisting of individuals of all 

 sizes. Here, at Oehrenstock, near Ilmenau, are % also found 

 the curious shapes of a parasitic formation, which present even 

 the slightest peculiarities of the crystallizations of calcareous 

 spar as to regular form, but consist of a tissue of crystals of 

 pyrolusite, and engaged in a mass of the same description. 

 From the mines of Ehrensdorf near Maehrisch Triebau in 

 Moravia, since their discovery in 1 798, many thousand hun- 

 dred weights of excellent ore have been annually procured. At 

 Ehrensdorf the pyrolusite occurs in large nodules or masses, I 

 could not learn in what rock. It resembles the Thuringian 

 varieties. In Thuringia it forms veins in porphyry, and is 

 often accompanied with heavy spar. It is remarkable that no 

 pyrolusite should have been found at Ihlefeld in the Hartz ; 

 at least there was no trace of it in all those collections which I 

 examined, if we except some thin masses in porphyry, and 

 slender crystals, evidently of the form of manganite, the super- 

 ficial layers of which yield a black streak, a circumstance 

 which has not yet received a satisfactory explanation. 



Pyrolusite is very often the product of decomposition of the 

 brachytypous parachrose-baryte, the carbonate of iron of the 

 latter being converted by the natural agents into the hydrate 

 of the peroxide, while the lime which it occasionally contains 

 is deposited in the shape of calcareous spar or Arragonite, and 

 the manganese is often found covering the surface of decom_ 

 posed rhombohedrons of the original species, in the shape of 



