OF ARKANSAS. 



1G3 



The amount of free oxygen was determined by Mohr's method to be 

 10.002 per cent. 



Taking into consideration the quantity of free oxygen contained in the 

 88.628 per cent, of manganoso-manganic oxide, we obtain for water, 

 expelled at a red heat, 0.G11 per cent.; hence, the composition of the 

 mineral may be expressed thus: 



Protoxide of manganese 82.448 



Free oxygen 10 002 



SiIica 5.329 



BaO'ta 0.282 



Lime 1.178 



Magnesia trace 



Water 0.611 



99.850 



No. 22. Wad, from near the North fork of White river, Izard county. 



A brecciated rock; the matrix consists of wad, in which angular pieces 

 of white chert are imbedded. The wad possesses the following physical 

 and chemical properties: 



Compact, amorphous; lustre dull, on rounded edges shining; color iron- 

 black; hardness 4; powder dark brownish olive-green. 



Heated on charcoal in reduction flame, turns reddish-brown; heated in 

 a matrass, yields water copiously, at a low heat. With fluxes gives the 

 reactions of manganese. Dissolves readily in hydrochloric acid, with 

 evolution of chlorine, and separation of silica. 



Having but a small specimen at my disposal, and the siliceous mineral 

 adhering very firmly to the ore, I could not collect enough of the pure 

 wad for the purpose of analysis, but was compelled to analyze the 

 mixture. 



The mixed minerals, dried at 220 deg. F., had the following compo- 

 sition: 



Manganoso-manganic oxide 51.365 



Silica 26.230 



Alumina, with trace of iron 6.245 



Oxide of cobalt 0.104 



Baryta 1.875 



Lime trace 



Water and oxygen, expelled by heat 14.889 



100.708 



