20 delations of Trap-I\ocks jvlth Ores of Copper. 



gree of alteration in the upraised formation and the schal- 

 stein.* 



One may study the different rocks of the formation by 

 going to the mines by the narrow road to the north-west of 

 Dillenburg, which runs along the side of the naked escarpe- 

 ments. We can distinguish the massive and undulated sur- 

 faces of the greenstone at a great distance, and, in the mine 

 heaps, the most varied specimens are to be found of the rocks 

 ti'aversed by the mine galleries, which are mostly pierced 

 perpendicularly to the direction of beds, so as to cut across 

 the whole of them. By the aid of plans of the mines, where 

 the different formations are marked in accordance with the 

 description of the metalliferous repositories, we gain a precise 

 knowledge of their mineralogical characters, and relative 

 position. 



In a mineralogical point of view, the schalstein, whose 

 characters are so variable, are the most interesting rocks. 

 We find among them brecciform varieties, with green or red- 

 dish angular fragments ; amygdaloidal varieties, with a mix- 

 ture of calcareous spar, which is sometimes in irregular veins, 

 sometimes in radiated globules ; lastly, we find among them 

 those green or red varieties, compact and homogeneous, 

 which throw so much uncertainty over the oi'igin of these 

 rocks. Among the rocks connected with the schalstein, and 

 having the same direction, we may mention the red peroxide 

 of iron, which forms irregular beds from 1 to 3 or 4 yards 

 in thickness. At the mine of Stangenwaage there is a thick 

 bed of this oligistic ii'on found on the roof of a bed of schal- 

 stein, and which exhibits all the peculiarities of position ob- 

 served in banks of oligistic iron subordinate to the blatterstein 

 of the valley of Lehi-bach, in the Harz. In the raining heaps 

 we are struck with the flat shape of all the fragments of 

 schalstein, and on examining the rock in situ, we perceive 

 that the principal fissures which produce this structure, and 



* There is still a further approximation to be noticed between the altered 

 rocks of Dillenburg and those of Tuscany. The two degrees of alteration are 

 represented in the two localities ; the first by the red slates of Nassau and the 

 red galestri of Tuscany ; the second by the schalstein and the gabbro. 



