70 
MANGANESE. 
A collection of minerals carrying manganese in commerci- 
ally available quantities. These are : 1st. Oxides of manganese, 
which include, besides several well marked mineral species a 
number of minerals almost indistinguishable from one another. 
Of these the most important are : Pyrolusite, the binoxide, with 
62.4 per cent, manganese. 
Manganite, the hydrous sesquioxide, with 62.4 per cent 
manganese. 
Psilomelane, another hydrous oxide of manganese, with 
manganese varying from 50 to 60 per cent. 
Braunite, the sesquioxide of manganese, with 69.68 per 
cent, manganese. 
Wad, which is a mixture of various oxides of manganese 
with other oxides, and has no definite composition. 
Minerals other than the oxides are: 
Rhodochrosite, the carbonate of manganese, with *47.8 per 
cent, manganese. 
Rhodonite, the silicate, with 41.9 per cent, of manganese. 
Franklinite, an oxide of manganese, zinc and iron, with 
from 7 per cent, to 23 per cent, manganese. 
Ores of manganese from many important mining districts. 
Especially to be noted are the ores from Santiago de Cuba^ 
which are typical, and those from New Jersey, which are unique 
n mineralogical character. Polished specimens of rhodonite 
from England, illustrate an occurrence utilized both as manga- 
nese ore and for ornament. 
In the two adjacent floor cases are large specimens of man- 
ganese ores. 
Iron ores fill six wall cases and one floor case. 
The case following the manganese ores contains iron ores of 
South America and Mexico. A full collection of iron ores and 
surrounding rocks of the Cerro Mercado or Iron Mountain, of 
Durango, Mexico, illustrates a valuable occurrence of an im- 
portant but little understood type of iron ore deposit. Large 
specimens of a specular hematite from the state of Minas 
Geraes, Brazil, in the lower portion of the case, illustrate the 
type micaceous hematite, of world-wide distribution. Many o-f 
the ores in this case represent deposits of ore almost unknown 
to the world at large. 
