228 GEOLOGY OF THE SECOND DISTRICT. 



Brown tourmaline occurs in some other localities in a mode quite unusual : it forms, for 

 instance, upon some smooth flat surface, as that of a crystal of scapolitc, a thin arborescent 

 pellicle, similar to a metallic deposition. Whatever it may be, or how formed, the material 

 appears to have been in solution after liie mass on which it exists had crystallized, and to have 

 spread upon the surface while consolidating. 



In the extreme west part of the town of Chester, a limestone range, in crossing a creek, 

 forms a natural bridge. The place is principally interesting from this circumstance, and the 

 large underground passages which have been worn out by the water. The locality is about four 

 miles from Chester corners, on the road to Minerva. 



Passintr now to the northwest part of the county, we find several beds of primitive lime- 

 stone, under nearly the same conditions as in the southern and eastern parts. Long pond is 

 one of the mo.st interesting : it is in the south part of Keene, about eight miles southeast of 

 the Elba iron-works, and four or five west from Miller's in the same town. This bed, or 

 rather vein, was brought to light by a slide from the mountain, which rises steeply from a 

 small sheet of water known in the vicinity by the name of Long pond. The vein is twenty 

 to forty feet wide, and occupies the highest part of the slide, being nearly half a mile from 

 the pond. It rises out of the hypersthene rock, in the form of an irregular vein, or more 

 properly a mass. It has the usual characters, but as a whole, is coarser. Some parts furnish 

 a fine blue calcareous spar. A fact worth mentioning, is that the blue portion is confined to 

 the surface, while the deeper situated is of a pale green ; but on exposure to light, the latter 

 also becomes blue. 



This locality furnishes undoubted evidences that the limestone is an injected mass, or, in 

 other words, a plutonic rock. The mineralogist will find at this place a rich locality of 

 pyroxene, in all its forms and varieties. In color, it varies from the darkest green to nearly 

 white. It is in fine glossy crystals, in perfect forms, and easily obtained by blasting the lime- 

 stone. Phosphate of lime, in tolerable good crystals, may also be obtained. Another mineral, 

 which resembles idocrase, is quite common ; it is in very small crystals, but it has not been 

 particularly examined. 



This limestone furnishes no tourmaline or feldspar : it is apparently more in the character 

 of a volcanic product, furnishing particularly those minerals which arc associated with lavas, 

 as the pyroxene, amphibole, phosphate of lime, idocrase, etc. ; while in other places the same 

 rock shows its analogy to granite, by containing tourmaline, feldspar, scapolite, etc. Where 

 the primitive limestone furnishes the latter minerals, it is in beds more widely extended, or 

 much larger than in the former case. It is well known to mineralogists that the narrow veins 

 of granite are more bountiful in fine minerals than the rock itself, when it occurs as one of 

 the principal masses over a widely extended territory ; in fact, under the latter form it is emi- 

 nently barren, except where it is traversed by veins of the same substance of a much later 

 period than the principal rock. In addition to the above minerals, we have found large regu- 

 lar crystals of scapolite, some of which now remain attached to the rocks, and are eight inches 

 in diameter. 



