8 MISER AND FAIRCHILD: HAUSMANNITE 



Elderhorst.*^ Nevertheless, it seems necessary to recognize the 

 possible existence in nature of a mineral with a composition cor- 

 responding to the formula Mn203; it must be extremely rare." 



Although a mineral with a composition corresponding to the 

 formula Mn203 may, as pointed out by Fermor, be present in 

 the Batesville district, its occurrence there is not believed by 

 the writers to be probable, in view of the facts and conclusions 

 brought out during the present investigation. Penrose, in a 

 footnote^ regarding the sample for his analysis, says, "The original 

 specimen contained inclusions of a massive or semi-crystalline 

 oxide of manganese, but the sample analyzed was carefully sep- 

 arated from this and was composed only of the coarsely crystal- 

 line parts." As he describes^" psilomelane as being a massive 

 mineral, and as psilomelane appears to be the only mineral that 

 is intimately associated with hausmannite, the "massive or 

 semi-crystalline oxide of manganese" in the sample for his analy- 

 sis may have been psilomelane. The samples for our two ac- 

 companying analyses (Nos. i and 2) consisted entirely of the 

 coarsely granular parts of the specimens so far as could be de- 

 termined by means of a pocket lens, but as previously stated 

 polished surfaces of the specimens show that it is not possible to 

 discard all of the psilomelane by this method. A mixture con- 

 taining about 60 per cent of hausmannite and 40 per cent of 

 psilomelane (corresponding to the formula 2Mn02.MnO) would 

 on analysis be found to contain manganese protoxide (MnO) 

 and oxygen (O) in the ratio of 2 to i , which is the ratio calculated 

 from the analysis given by Penrose. As specimens are common 

 showing a gradation from psilomelane with only a small amount 

 of hausmannite in it to coarsely granular hausmannite with a 

 very small percentage of psilomelane, a sample containing the 

 above-mentioned percentages of these minerals could be ob- 

 tained, but such a sample, it must be admitted, could be ob- 

 tained only by accident. 



* D. D. Owen. First report of a geological reconnaissance of the northern counties 

 of Arkansas, 164-165. 1858; R. A. F. Penrose, Jr., op. cit., pp. 149-150. 

 ^ R. A. F. Penrose, Jr., op. cit., p. 148. 

 '" Idem, 145. 



