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uncommon beauty. It follows the eastern base of Pimple Hill to 

 the southwestern termination of that ridge, and then appears nearly 

 in the same line at several points on the west of the gneiss hills, 

 west of Sparta, and also within a few hundred yards of the 

 town itself. The narrow valley embraced between those hills 

 and the Wallkill Mountain on the southeast, is in the immediate 

 neighbourhood of Sparta, and for some distance southwest, 

 occupied by the unaltered blue limestone dipping usually towards 

 the northwest. 



About a third of a mile northwest of Sparta, the white crystal- 

 line limestone crosses the turnpike road. This is one of the prin- 

 cipal localities whence mineralogists have supplied their cabinets 

 with specimens of condrodite or Brucite. A better locality, how- 

 ever, may be seen on the west side of the hill, about half a 

 mile further north, where another exposure of the white crystal- 

 line limestone affords crystals of the Brucite and gray spinelle in 

 an abundance and of a quality far surpassing those of any other 

 spot yet discovered in this vicinity. At the same place might be 

 opened inexhaustible quarries of variegated and pure white mar- 

 ble; some of the former promising to be, if polished, of uncommon 

 beauty. Care should be observed, in establishing quarries in this 

 rock, to choose those parts of the belt least shattered by the 

 action to which it has been exposed. 



Between three and four miles southwest from Sparta, on the 

 northwest side of a low ridge of gneiss, we find a very interesting 

 locality of the altered limestone, very nearly in the prolongation 

 of the belt which passes along the southeast base of Pimple Hill. 

 This spot is remarkable less for the extent or breadth over which 

 the limestone has been affected by igneous action, than for the 

 strikingly convincing evidence which it affords of the nature of 

 the changes induced in the calcareous rock by the series of ig- 

 neous veins and dykes which we have been tracing. The ridge 

 itself, along the side of which the limestone has been altered, con- 

 sists chiefly of a thinly-bedded micaceous gneiss. Through the 

 summit, or rather on the northwestern flank, which is often ab- 

 rupt and rugged, there rises a thick granitic dyke or vein of very 

 heterogeneous composition, supporting the steeply-dipping beds 

 of gneiss, whose usual inclination is at an angle of 80° to the 



