258 METALS. 



15. MANGANESE. 



^^^* The ores of manganese have a specific gra\ily below 5*2. 

 They afford a violet-blue color with borax or salt of phos- 

 phorus, in the outer flame of the blowpipe ; and on heating 

 the oxyd with muriatic acid, fumes of chlorine are given out 

 which are derived from the acid. 



RHODONITE. — MANGANESE SPAR. 



Monoclinic ? In oblique rhombic prisms, isomorphous with 

 pyroxene ; usually large massive, the cleavage often indistinct. 

 Possibly triclinic, and the same as Fowlerite. 



Color reddish, usually deep flesh-red ; also brownish, 

 greenish, or yellowish, when impure ; streak uncolored. 

 Luster vitreous. Transparent to- opaque. Becomes black 

 on exposure. H = 5-5—6-5. Gr=3'4 — 3*7. 



Composition : oxyd of manganese 52*6, silica 39*6, oxyd 

 of iron 4*6, lime and magnesia 1*5, water 2*7. The impure 

 varieties, Bustamile, Photizite, and Allagite, contain varia- 

 ble proportions of carbonate of iron, lime, or manganese, 

 beside alumina. Becomes dark brown when heated, and fuses 

 with borax in the outer flame, giving a hyacinth red globule. 



JJif. Resembles somewhat a flesh-red feldspar, but dif- 

 fers in greater specific gravity, in blackening on long expo- 

 sure, and in the glass with borax. 



Obs, Occurs in Sweden, the Hartz, Siberia, and else- 

 where. In the United States it is found in masses, at Plain- 

 field, and Cummington, Mass. ; also abundantly at Hinsdale, 

 and on Stony Mountain, near Winchester, N. H. ; at Blue 

 Hill Bay, Me. The black exterior is a more or less pure 

 hydrated oxyd of manganese. 



Uses, Dr. Jackson has suggested the use of this ore for 

 making a violet-colored glass, and also for a colored glazing 

 on stone ware. The finely pulverized mineral, spread on 

 stone ware as a paste, will afford a permanent glazing, 

 which will have a black color if it be of considerable thick- 

 ness, and of a deep violet-blue if quite thin. It may be 

 used along with the usual salt glazing. 



What is said of the ores of manganese ? What is the appearance 

 of manganese spar ? its composition and blowpipe characters ? Ho* 

 is it distinguished from feldspar ? For what may it De used] 



