106 MINERAL PRODUCTS 



§ 1. Brown hematite, and oxide of manganese^ 



The hrown hematite and oxide of manganese are associated in the same beds, and are 

 derived from sources originally the same. I have ah-eady stated that the Stockbridge lime- 

 stone often passes into thin talcose strata, in which a peculiar ferruginous looking sub- 

 stance abounds. These layers, by exposure to the atmosphere, become yellow from the 

 presence of ochre which appears diffused through them. But they alwaj's disintegrate 

 rapidly, and form deep yellow clays, which, on being penetrated, furnish nodules of oxide 

 of iron ; or, in places where there is a great accumulation, beds of the ore are found lying 

 wholly disconnected with the rock in the common acceptation of the word. In some in- 

 stances the ore is collected in beds in a (ine drift, or soft material containing round pebbles, 

 frequently granular (piartz, and occasionally stockbridge limestone. It is difficult to de- 

 termine whether the materials forming these beds have been transported or not. They 

 appear to have been carried into depressions by the slow operation of common or ordinary 

 causes, simultaneously with the disintegration and decomposition that detached and sepa- 

 rated the particles from their common matrix. The beds thus formed may have been 

 enveloped in drift, with the partial destruction of the accumulated materials. 



The hematite embraces the usual varieties of imitative forms, as botryoidal, mammillary, 

 stalactitic, etc. Large globular hollow masses are often met with in the excavations, of 

 sufficient capacity to hold a barrel of water, and sometimes water is found in them. The 

 interior of these large globes is lined with a splendent coating of manganesian matter, 

 spread over the vertical fibres which terminate inwards. The outside is always rough with 

 projecting points of hardened ore. 



The manganese is usually collected in masses amidst the iron ore : it is in imperfectly 

 compacted masses, or in that condition called wad. In other instances, it is in hard rough 

 black masses, with a fine granular or earthy textiuc ; and sometimes in fine needleform 

 crystals of exceedingly high metallic lustre. 



A range of beds of hematite extends from Westchester county, through Salisbury, 

 Amenia, Stockbridge, Richmond, Bennington, and onwards to the Canada line. All 

 the independent ranges of the Taconic rocks furnish beds of hematite. 



Associated with the same beds is the gibbsite, an aluminous mineral occurring in the 

 form of incrustations, and pendent among the masses of ore in stalactites or tuberous 

 masses. Fine white clays also abound, which appear of the same composition as the 

 gibbsile. White carbonate of iron is also quite common, usually in rounded or kidney- 

 form masses. 



The difl^erent minerals enumerated above are derived from the magnesian slates and 

 limestones, and not from the taconic slate. 



