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black homogeneous rock of the nature of trap. Veins of 

 quartz are not uncommon. Small granular crystals of 

 epidote are seen upon the surface, and we are inclined 

 to think that the mass of rock is coloured by this mineral. 



Between the villages of Paris and Salem, in Fauquier 

 county, various altered rocks occur. They are similar 

 in appearance to certain traps; again they are of the 

 nature of grits, passing into protogine and other hetero- 

 geneous rocks, in which the quartz predominates. At 

 the distance of about five miles from Salem, you come 

 upon shales that are neither talcose nor argillaceous 

 schists, but appear to be mixtures of either. Much 

 quartz in veins traverses these beds. 



At the distance of four miles from Salem, there is a 

 green petro-silicious rock with crystals of feldspar. The 

 base varies in colour, generally a dirty green, and the 

 lamellar feldspar sometimes very abundant. This rock 

 contains veins of quartz of a dark blue colour which is 

 a very beautiful variety. The trappites hereabout have 

 a general dark green hue. The dark blue quartz is so 

 common, that the fences have been partially constructed 

 with this material. 



In approaching Salem, the amphibolic rocks, with re- 

 peated modifications, occur; and sometimes the amphi- 

 bole nearly disappears, and you have a ferruginous grit. 

 These amphibolic substances are not unfrequently schis- 

 tose, more generally massive, compact, hard, and fre- 

 quently disintegrating upon the surface, which renders 

 it difficult to get a perfect idea of the nature of the sub- 

 stances which compose the mass. As you leave Salem 

 and proceed east towards Warrenton, the modified am- 

 phibolic rocks continue until you come upon a dark, and 

 a lighter gritty rock. Talcose slates, with quartz veins, 

 now become common; and the whole surface of the coun- 

 try, from this, for several miles beyond Warrenton, is 

 parscmated with milky quartz. Those traps already 

 I.— 2 o 



