ORDER VIII. PRISM ATOIDAL MANGANESE-ORE. 



reed-like prisms, and such massive varieties as consist of 

 columnar particles of composition, while the foliated one 

 refers to short prisms and granular compositions. Compact 

 Grey Manganese-Ore contains varieties, composed of im- 

 palpable granular individuals ; and Earthy Grey Manganese- 

 Ore, such as have lost their coherence, and appear in the 

 state of an earthy powder. 



2. The composition of some varieties, belonging to pris- 

 matoidal Manganese-ore, has been found by KLApaoTHtobe 



Black Oxide of Manganese 90-50 89-00. 



Oxygen 225 10-25. 



Water 7'00 0-50. 



It is infusible before the blowpipe, and colours glass of 

 borax violet-blue. It is insoluble in nitric acid. In heat- 

 ed sulphuric acid it disengages oxygen, and chlorine is 

 disengaged, if it is brought in contact with muriatic acid. 

 Also before the blowpipe, or alone in a strong heat, it gives 

 out oxygen. 



3. The present species frequently accompanies prismatic 

 and rhombohedral Iron-ore ; sometimes its earthy varieties 

 constitute beds by themselves. It occurs often in veins, 

 particularly in porphyry, along with prismatic Hal-baryte. 



4. Several varieties of the species generally occur to- 

 gether. They occur in abundance and great beauty at 

 Ihlefeld in the Hartz, and at Oehrenstock near Ilmenau in 

 Thuringia. But they are found likewise at Johanngeorgen- 

 stadt and Eubenstock in Saxony, at Flatten in Bohemia, in 

 several places in Hungary, in Moravia, Silesia, and France. 

 They are met with also in different localities in England 

 and Scotland. 



5. The prismatoidal Manganese-ore is a useful mineral 

 in the manufacture of glass, and painting in enamel. It 

 is likewise essential in several chemical operations. If 

 found along with iron-ores, it is said to be favourable to the 

 quality of the iron extracted from the latter. 



6. Black Wad, to which probably Brown Iron-Froth will 

 be found to belong, deserves to be mentioned in the pre- 

 sent place as a very remarkable mineral among those which 



