Dr Turner's Chemical Examlnatwn of Wad. 215 



be presently described, and two minerals noticed in my former 

 communication, — the baryta is unquestionably united with an 

 oxide of manganese less highly oxidized than the peroxide. 

 The presence of such a compound in the Derbyshire Wad will 

 readily account for the oxygen being somewhat less than 

 theory requires. 



The hydrated peroxide of manganese may thus be regarded 

 as the essential ingredient of the Derbyshire Wad, and, accord- 

 ing to my observation, is the most frequent variety of this 

 mineral. I have not met with it in a state of perfect purity. 

 It usually contains small quantities of some other oxide of 

 manganese, together with barytaj oxide of iron, lime, and silica. 



Mr Konig has kindly supplied me with two other varie- 

 ties of this Wad, one from Huttenberg in Carinthia, and the 

 other from the district of Nassau. They agree with the Der- 

 byshire wad in all their physical properties, except in the 

 small micaceous particles being less compacted together, and 

 the fibrous arrangement being more distinct. They yield also 

 by analysis similar quantities of red oxide of manganese, oxy- 

 gen, and water. They both contain traces of silica and 

 baryta ; and a little lime was detected in the latter. A varie- 

 ty of Wad from the neighbourhood of Elbingerode in the 

 Harz, sent me by Professor Hausmann of Gottingen, under 

 the name of schaumiges or frothy Wad, belongs to the same 

 species. The greater part of it was in powder ; but the co- 

 hering particles had the same physical characters as the pre- 

 ceding. It is identical also in chemical constitution, and con- 

 tains traces of siliceous matter, baryta, and oxide of iron. I 

 have received another variety of the same mineral, under the 

 name of earthy ochreoiis Wad, from Professor Stromeyer. It 

 occurs in the district of Nassau ; and though essentially iden- 

 tical with the preceding varieties, is much less pure. It is 

 visibly intermixed with the hydrated red oxide of iron, and 

 when dissolved in muriatic acid leaves a considerable quantity 

 of earthy insoluble matter. 



Second species. Wad from Derbyshire. 



This Wad, for which I am indebted to Mr Konig, is earthy 

 without the slightest crystalline appearance. It acquires a 

 shght lustre by friction, but is otherwise dull. It is very soft 



