ORIGIN. 



edly the equivalent of those already described, along the western base of the Green Mountains. Most 

 likely the quartz and limestone once extended over the mountain, and were subsequently denuded. As the 

 limestone extends north into Sherburne, probably hematite may also be found there. 



Whether the quartzose breccia in Hartwellville, near the crest of the Green Mountains in that place, 

 should be reckoned among the hematite deposits already described, is doubtful. The cement is doubtless 

 hematite ; but there are no signs of limestone, or quartz, or of the white and variegated clays. The great 

 height, also, above the ocean, seems to separate it by a wide interval from the other beds. And yet it must 

 have resulted from the same agencies as the other hematite beds, but perhaps not at the same geological 

 period. 



The origin of these beds is a difficult subject for the geologist. We find them, almost 

 without exception, associated with metamorphic limestone, quartz rock, which is perhaps 

 metamorphosed sandstone, and with mica schist, which has also been metamorphosed. 

 But from which of these rocks was the iron derived ? For in general its present position 

 is the result of the action of water, which has worn it off from the subjacent rocks, and 

 re-deposited it in connection with clay, sand and gravel. In a few instances, however, 

 we find it in the rocks. At west Stockbridge in Massachusetts, the bed of ore with 

 interstratified clay has not lost the marks of original stratification. It seems to be 

 merely a mass of metamorphosed mica schist, and in the northeastern part of Connecti- 

 cut, as well as the eastern part of New York, in the same latitude, we have seen beds of 

 hematite lying between strata of mica schist. (See Final Report on the Geology of 

 Massachusetts, p. 584.) 



To ascertain whether the iron did not result from the disintegration of the associated 

 limestone, Mr. Gr. F. Barker was kind enough to furnish the following analysis of the 

 limestone underlying the hematite of Brandon. 



Carbonate of Lime, . . . 40.88 



Carbonate of Magnesia, . . .51.40 



Carbonate of Iron, . . . 3.61 



Quartz and other insoluble matter, 3.44 



99.39 



East of the Brandon bed is a limestone used as a flux, that contains 10 per cent of 

 iron. It is obvious then that the limestones may have furnished the whole or a part of 

 the iron. But its occurrence in the limestone, and as beds in mica schist, leads rather to 

 the conclusion that in part such may have been the origin of the hematite. Indeed, we 

 are of the opinion that the ore was derived from both the rocks, and possibly, also, in 

 some cases from the quartz rock. It is now well understood that the different species of 

 iron ore undergo changes naturally in the earth from one into the other. Starting with 

 carbonate of iron, it is changed into hematite hydrous and anhydrous ; then into specu- 

 lar iron, then into the magnetic protoxyd. At the surface all the other ores of iron are 

 apt to pass into hematite ; and in the earth, below the influence of the atmosphere, into 

 magnetic iron. (See Bischofs Chemical and Physical Geology, Vol. II, p. 53. Also Lesley's 

 Iron Manufacturer's Guide, Chapter II, Part II.) 



Now it is well kno,wn that all the species of iron ores above mentioned, and also the 

 sulphuret, occur in the rocks that underlie the hematite, or are not far from it. The 

 carbonate exists, as we have seen, in the limestone beneath the hematite beds, also in the 



