252 



Geology of the Neilgherries. 



[No* 12, new SERIES, 



Black Manganese ore, combination of manganese, oxygen, water, 

 silica, and iron. Magnetic after roasting. With borax gives a 

 violet bead. In the bulb disengages water. Massive and botry- 

 oidal. Leaves a shining streak on paper. Is scratched by the 

 snife and leaves a shining streak under it. Colour — blueish black, 

 opaque. Fracture earthy. Berthier states this ore contains 70 

 per cent, of manganese ; all the ores of this metal afford from 65 

 to 85 per cent, with the exception of the silicate of manganese 

 which has but 50. When the manganese ore found at Coonoor is 

 dissolved in muriatic acid, and exposed to heat, copious fumes of 

 chlorine are evolved. I failed to obtain a precipitate of sulphate 

 of barytes from the solution, on testing with sulphuric acid, al- 

 though barytes is usually found in combination with this form of 

 manganese. Accompanying this ore I found that beautiful variety 

 of brown iron ore called, brown hematite, fibrous brown iron ore. 

 Color — blackish brown. Structure — fibrous and radiating. Lustre 

 silky, botryoidal, mammillary, stalactitic. Iridiscences occur in 

 some of the specimens. Brittle. 



While speaking of brown iron ore I make the opportunity sub- 

 serve to describe two varieties I observed near Ootacamund. Sta- 

 lacmitic brown iron ore (hydrate of iron) arises in a deposit from 

 water strongly impregnated with iron, and is probably the same 

 with the morasterz of the Germans though more indurate. Occurs 

 in stalacmitic beds 2-10 of an inch thick in banks below the ve- 

 getable soil. To the lower side of these plates, when they are 

 drawn out of the bank, are found small stalactites depending. 



This ore is a hydrate of iron with a considerable quantity of 

 allumina and silica. Is raised by the magnet after roasting. 

 Stalactitic brown iron ore (hydrate of iron), about which DeBenza 

 spent so much time and thought in endeavouring to account for its 

 tubular form conceiving the tubes owed their origin to capillary 

 attraction, in other words making the stalactites grow upwards in- 

 stead of downwards. The stalactite is formed by the percolation 

 of water containing iron. It has long been known as one of the 

 commonest forms of this ore. This mineral is raised by the mag _ 

 net after roasting. 



Jaspery iron— a variety of red iron ore I also now add to the 

 list of the ores of iron. 



