OF ARKANSAS. J 53 



it has certainly been derived from the red clay, filling the cavities of the 



ore. 



No. 9. Compact smithsonite, incrusting dolomite. 

 Composition, dried at 212 deg. F: 



°- uartz 1.512 



Oxide of zinc Gr , 907 



" iron trace 



Lime ; 1.067 



Magnesia trace 



Carbonic acid, and loss 31.454 



100.000 

 The air-dried mineral lost 0.1 1G per cent, of moisture at 212 deg. F. 

 From the high per centage of oxide of zinc in this mineral, it would 

 appear to be a basic carbonate of zinc, but as no direct carbonic acid 

 determination was made, it is not, at present, possible to construct a for- 

 mula for its composition. 



Rounded pieces of dark-gray, subcrystalline dolomite appear, sometimes, 

 as if cemented by carbonate of zinc, which surrounds the fragments in 

 concentric, incrusting layers. The carbonate of zinc is of grayish, brown- 

 ish, or reddish color; between its layers, but mostly between the dolomite 

 and the carbonate of zinc, a white mineral is occasionally observed, whose 

 properties and composition are given in No. 10. 



No. 10. Maiuonite, a new hydrous carbonate of zinc. 



Occurs in concentric and contorted lamina?, also, in botryoidal and mam- 

 milated incrustations; amorphous; earthy; color milk-white; hardness 2.5; 

 easily reduced to powder; powder milk-white. 



Dissolves readily, and completely, in cold dilute hydrochloric acid, with 

 effervescence; also, when pulverized, in ammonia; in both solutions, sul- 

 phydrate of ammonia produces a white precipitate. Heated in a matrass, 

 yields water and turns yellow; heated before the blowpipe with a solution 

 of nitrate of cobalt, assumes a bright green color; on charcoal, behaves like 

 oxide of zinc. 



On being ignited in a platina capsule, the mineral lost 26.818 per cent; 

 the residue, dissolved in hydrochloric acid, and the solution precipitated 

 with carbonate of soda, gave 73.262 per cent, of oxide of zinc. 



Carbonic acid and water 26.818 



Oxide of zinc 73.262 



100.080 



