MANGANESE ORES. 



259 



It receives a high polish, and is sometimes employed for 

 inlaid work. 



Tephroitc. A silicate of manganese, occurring massive and cleavable. 

 Color ash-gray. H=5*5. Gr=4. From Franklin, N. J. Compo- 

 sition : silica 29'8, Tirotoxyd of manganese 70*2. Fuses easily to a 

 black scoria. Knebelite is a related species. 



Fowlerite (Paisbergite). Probably same as Rhodonite. Form tri- 

 dinic. In crystals at Franklin, N. J., and FJaisberg, Sweden. 



pyrolusite — Binoxyd of Manganese. 



Trimetric. In small rectangular prisms, more or less 

 modified. M : M=93' 40 ; M : e=* 

 136 3 50'. Sometimes fibrous and ra- 

 diated or divergent. Often massive 

 and in reniform coatings. 



Color iron-black ; streak black, un- 

 metallic. H=2— 25. Gr=4-8— 5-0. 

 Composition: essentially the bin- 

 oxyd ot manganese, consisting of oxygen 37, and manganese 

 63. With borax it gives an amethystine globule. It yields 

 no water in a matrass. 



Dif. Differs from psilomelane by its inferior hardness, 

 and from ores of iron by the violet glass with borax. 



Obs. This ore is extensively worked in Thuringia, Mo- 

 ravia, and Prussia. It is common in Devonshire, Somerset- 

 shire, and Aberdeenshire, in England. In the United States 

 it is associated with the following species in Vermont, at 

 Bennington, Brandon, Monkton, Chittenden, and Irasburg ; 

 it occurs also in Maine, at Conway, and Plainfield, in Mas- 

 sachusetts ; at Salisbury, and Kent, in Conn., on hematite. 



The name pyrolusite is from the Greek pur, fire, and luo, 

 to wash, and alludes to its property of discharging the brown 

 and green tints of glass, for which it is extensively used. 



Uses. Besides the use just alluded to, this ore is exten- 

 sively employed for bleaching, and for affording the gas oxy- 

 gen to the chemist. 



PSILOMELANE. 



Massive and botryoidal. Color black or greenish-black. 

 Streak reddish or brownish-black, shining. H =5—6. Gr= 

 4—4-4. 



Describe pyrolusite. What is its constitution 1 What are its uses 1 

 Describe psilomelane ? How does it differ from r. yrolusite. 



