254 EEPOET OF NATIONAL MUSEUM, 1899. 



manganese ores, in Thuringia; is also found in the Harz Mountains; 

 Wermland, Sweden, and various other European localities. In the 

 United States it is reported as occurring only in Iron County, Missouri. 

 The mineral in its ideal purity consists of sesquioxide and protoxide 

 of manganese in the proportion of (^)9 parts of the former to 31 of the 

 latter. Analyses of the commercial article as mined are not at hand. 



Braunite. — This, like hausmannite, crystallizes in the form of the 

 octahedron, but is a trifle harder. Chemically it differs, in that 

 analyses show almost invariabl}^ from 7 to 10 per cent of silica, 

 though as to whether or no this is to be considered an essential con- 

 stituent it is as yet difficult to say. Analyses 1 and 2, on p. 256, show 

 the composition of the mineral as found. The ore is reported as 

 occurring both crj^stallized and massive in veins traversing porph^ay 

 at Oehrenstock in Ilmenau, in Thuringia, near Ilefeld in the Harz; 

 Schneeberg, Saxony (Specimen No. 68136, U.S.N.M.), and various 

 other European localities. Also at Vizianagram in India; in New 

 South Wales, Australia, and in the Batesville region, Arkansas. 



PoLiANiTE. — Like pyrolusite, 3'et to be noted, this form of the ore is 

 chemically a pure manganese binoxide, carrying some 63.1 per cent 

 metallic manganese combined with 36.9 per cent oxygen. From 

 pyrolusite it is distinguished by its anhydrous character and increased 

 hardness. So far as reported, it is a rather rare form of manganese, 

 though possibly much that has been set down as pyrolusite ma}^ be in 

 reality polianite. 



Pyrolusite occurs in the form of iron black to steel gray, sometimes 

 bluish opaque masses, granular, or commonly in divergent columnar 

 aggregates sufficiently soft to soil the fingers, and in this respect easily 

 separated from the other common forms excepting wad. Not known 

 in crj'stals except as pseudomorphs after manganite. Its composition 

 is quite variable, usually containing traces of iron, silica, and lime and 

 sometimes barium and the alkalies. Analyses III and IV, on p. 256, as 

 given by Penrose, will serve to show the general average. This is a com- 

 mon ore of manganese, and is extensively mined in Thuringia, Mora- 

 via, Bohemia, Westphalia, Transylvania, Australia, Japan (Specimen 

 No. 61936, U.S.N.M.), India, New Brunswick (Specimen No. 36825, 

 U.S.N.M.), Nova Scotia, and various parts of the United States 

 (Specimens Nos. 42011, Tennessee, 56354, Georgia, etc.). 



Manganite differs and is readily distinguishable from the other 

 ores thus far described, in carrying from 3 to 10 per cent of combined 

 water, which can readily be detected when the powdered mineral is 

 heated in a closed tube. From either psilomelane or pyrolusite it is 

 distinguished by its hardness. When in ciystals it takes prismatic 

 forms with the prism faces deeply striated longitudinall}^ (Specimen 

 No. 67922, U.S.N.M., from Thuringia). Its occurrence is essentially 



