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Near liockwood, not far out of the general line of the larger 

 belts or ridges of the crystalline limestone already treated of, we 

 come upon another band of the calcareous rock which has 

 undergone alteration. Though of rather local extent, this spot 

 is deserving of attention, if only for the perfection in which we 

 here behold the translucent rhombic spar, into which the blue 

 sedimentary limestone has been converted by the agency of heat. 

 Disseminated through the spar, we find the graphite sometimes 

 in regular hexagonal plates half an inch in diameter. From a 

 large rhombic crystallization, the calcareous rock graduates to 

 an amorphously crystalline limestone, or a white granular marble. 



Some portions of the mass, especially those having the more 

 highly developed crystalline character, include, besides the 

 graphite, several minerals, as Brucite, mica, talc, quartz, and green 

 spinelle ; the mica being in some cases so abundant, as to imply 

 probably its derivation from the contiguous gneiss rocks. 



While alluding to the vicinity of Lockwood, it may be men- 

 tioned as an interesting locality of granular and crystalline augite. 

 Some of the beds of the gneiss in this neighbourhood, being 

 traversed by bands of a deep-green talcose mineral, pervading a 

 mass consisting chiefly of lighter-coloured felspar, would furnish 

 a building material of very beautiful appearance. 



Having now described in sufficient detail the numerous bands 

 of altered limestone comprehended in the one general belt of 

 igneous action, which stretches in a nearly straight direction 

 from beyond Amity, in New York, to its southwestern termination 

 near Andover Forge, a little beyond Lockwood, 1 shall in the 

 next place enter upon a more brief account of the shorter, but 

 no less interesting belt, which pursues the southeastern base of 

 Jenny Jump. 



As in the instance of the altered rock near the eastern foot of 

 Pochuck Mountain, the beds of the white crystalline limestone of 

 Jenny Jump do not lie against the flank of the hill itself, but 

 belong to a separate low narrow ridge, or rather series of ridges, 

 parallel with its base, but at a distance sometimes of a few 

 hundred feet. These ridges consist in part of the altered rock, 

 and in part of a succession of intrusive dikes of what, from its 

 general aspect and composition, may be termed a sienite rock, 



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