2G2 KEMP'S ORE DEPOSITS. 



COBALT (SEE UNDER "NICKEL"). 



MANGANESE. 



2.14.14. Ores: Pyrolusite MnO 2 , Mn. 63.2, braunite, Mn. 2 O 3 , 

 Mn 69.68. Some SiO 2 , which may be chemically combined, is 

 usually present, and small amounts of MgO, CaO, etc. Psilome- 

 lane has no definite composition, but usually contains barium or 

 other impurities. An Arkansas variety has afforded Brackett 

 MnO, VV.85. 



There are various other oxides and hydroxides, which are rare- 

 ly abundant enough to be ores. The carbonate, rhodochrosite, 

 and the silicate, rhodonite, are rather common gangue minerals 

 with ores of the precious metals. Franklinite is also an important 

 source (2.07.04). Pyrolusite and psilomelane are the commonest 

 ores the country over, but braunite is the one in the Batesville 

 (Ark.) region. Manganese is widely distributed, and yet is com- 

 mercially important in but few localities. It imitates limonite 

 very closely in its occurrence and is often associated with this ore 

 of iron. To make a manganese ore valuable, at least 40$ metallic 

 manganese should be present, and this is a lower limit than was 

 formerly admissible when the ores were chiefly used in chemical 

 manufactures. Under present conditions, if iron is present, the 

 ore may be suited to spiegel, although even lower in manganese 

 than 401 Further, there should be low phosphorus ; Penrose 

 says not over 0.2 to 0.25$ in Arkansas, and not over 12$ SiO 2 . 

 High-grade ores run 50 to 60$ manganese. 



2.14.15. Example 50. Manganese ores, chiefly psilomelane 



serpentine along the State line near Delaware. D. T. Day, Mineral Re- 

 sources of the U. S., 1882, p. 428 ; 1883-84, p. 567 (Rec.) ; 1885, p. 357 ; 1886, 

 p. 176 ; 1887, p. 132. J. Eyerman, " On Woods Mine, Pennsylvania," Min- 

 eralogy of Penn.j Easton, 1889. P. Eraser, "The Northern Serpentine 

 Belt in Chester County, Pennsylvania," M. E., XII. 349. Rep. C3 (Lan- 

 caster County), Penn. Geol. Survey. T. H. Garrett, "Chemical Examina- 

 tion of Minerals associated with Serpentine," Amer. Jour. Sci., ii., XIII. 

 45, and XV. 332. Also F. A. Genth, Amer. Jour. Sci., ii., XLI. 120. E. 

 Goldsmith, " Chromite from Monterey County, California, "Phil. Acad.Sci., 

 1873, p. 365. William Irelan, Jr., Reps. Cal. State Mineralogist, especially 

 1890, pp. 167, 189, 313, 582, 583, 638. G. H. Williams, "The Gabbros and 

 Associated Hornblende Rocks near Baltimore," Bull. 23, U. S. Geol. Sur- 

 vey, pp. 50-59. " The Geology of the Crystalline Rocks near Baltimore," 

 distributed at the Baltimore meeting of the Institute of Mining Engineers, 

 February, 1892. Rec. 



