OF ARKANSAS. 163 
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 ared heat, 0.611 per cent.; hence, the composition of the 
mineral may be expressed thus: 
Protoxide of manganese +++-+++++++++++ 82.448 
Free oxygen: ++++seeees seeerenvereeoee 10.002 
Aces eR ee ee 5.329 
Baryta::+ tee eeeees ree 0.282 
Lime--.-+c.eee cae any 1.178 
Magnesia +++-+++++- ‘ cane tases trace 
Water--.-+-» eB ua oh 6 dearer a aloce e etiee eae Sih 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: ss essere eect ence eeeeeneneneeens 26,230 
Alumina, with trace of iron-++++++s+e+- 6.245 
Oxide of cobalt. +... +see+0: wen eeens vee 0,104 
Baryta: +++ o- see eeeeas teneees 1.875 
Lime--t-ssee VEG bee) Ba eee err ar trace 
Water and oxygen, expelled by heat-+.-- 14.889 
100.708 
