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been opened in many places, and furnish a material for building 

 which can hardly be excelled either for strength or permanency un- 

 der exposure. Much of this rock, however, is so hard as to prove 

 difficult of separation in the quarry. This is remarkably the case 

 with the green variety, which occurs very abundantly for a mile or 

 two east of Meriwether's bridge on the Rivanna. This rock bears 

 the strongest marks of intense igneous action in its flinty hardness, 

 and in the large quantity of green epidote which has been developed 

 throughout its structure. It is, moreover, always intersected by 

 veins of quarte, so that it would be difficult to find a mass of con- 

 siderable size, in which many of these veins would not be visible. 

 It is further to be remarked, that always in the vicinity of these 

 quartz veins, the rock is hardest, and displays the largest portion of 

 the green colouring material. All these facts would seem clearly to 

 point to the quartz, as having been directly concerned in the various 

 modifications which the rock has obviously undergone. In further 

 illustration of this view, it may be added, that often in the immediate 

 neighbourhood of the veins of this material, asbestos, iron pyrites 

 and other minerals occur, which are known to be thus developed in 

 various rocks by veins of intensely heated matter injected into them 

 in a state of fusion. At Meriwether's bridge and in many other 

 localities along the range, the greenish-blue rock is studded with 

 black and greenish spots, indicating an incipient crystallization, and 

 clearly referable as the geologist would at once perceive, to the 

 agency of which we have spoken. Here, as well as in all places 

 where similar evidences of igneous action can be traced, the dip of 

 the rock becomes confused in consequence of the occurrence of nu- 

 merous cross joints, such as are often produced in stratified rocks 

 by an action of this nature. 



The gray and yellowish-red sandstone, occurring in beds some- 

 times of considerable breadth, and traversing the country in the 

 general range of rocks to a considerable distance, arc found in many 

 places to furnish quarries of very valuable building material. Such 

 of these beds as are intersected by frequent veins of quartz, are 

 found to be by far the hardest and most valuable. In the same bed, 

 examined at points some distance asunder, a great difference in the 

 hardness and consequent value of the material, may frequently be 

 observed. Thus, the bed which on the eastern flank of Peter's 

 mountain, near Gordonsville, yields a building stone which comes 

 from the quarry in long quadrangular blocks of great hardness and 



