oj Boston and its Vicinity 



199 



Geuus IV. — Manganese. 



SPECIES I — EARTHY OXIDE OF MAAVAXESE. 



Earthv Oxide of Manganese, Cleaveland, p. 547. Friable Black Manganese 

 Ore or Wad, Jameson, vol. ii. p. 461, from Dr. Reuss. 



External Characters, 



1 



Its colours are brown and grey. Of brown, it occurs blackish 



brown 



and of grey, dark blackish grey 



Its lustre is faintly glimmering and is resinous. 

 It occurs dendritick, and in mamillary incrustations. 

 It adheres to the tongue. 

 It soils. 



The streak is dark liver brown. 

 It is slightly friable. 

 It is semi-hard. 



The fracture is fine grained uneven and earthy. 

 It is brittle. 



It is very easily frangible. 



The fragments are indeterminately angular and rather blunt- 



edged. 



Its specifick gravity is about 2. 



Chymical Characters. 



Before the blowpipe it melts into a black si 

 d with Borax, communicates to it a violet ting 



5 



d when fas- 



Geological Situation and Localities, 



It occurs in beautiful dendritick impressions on, and investing 

 Petrosilex, in Milton j the coating is sometimes half an inch in 

 thickness; also investing Sienite^ at Lynn. 



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