CONVERSION OF CARADOC SANDSTONE INTO QUARTZ ROCK. 



227 



above described ; and in place of beds of sandstone we there find them suddenly changed 

 into a serrated pile of arid quartz rock of exceedingly picturesque forms, (the Sharp 

 stones) rising to about seven, hundred feet above the sea, and in which nearly all 

 traces of bedding have been destroyed, the lines of stratification, which can be defined, 

 being inclined at very high angles. 



Again, if we track the older strata of the same formation upon their strike from the 

 quarries of Frodesley and the Hoar Edge, to their contact with the trap of the Little and 

 Great Caradoc, we meet with precisely the same phenomena, the evidence in this case 

 being still more decisive. In the sandstones, at a certain distance from the trap, the 

 mechanical form of the grains of quartz is very evident, and they are associated with 

 much disseminated felspar. On the north-east side of Little Caradoc, or rather between 

 that hill and the Lawley, the sandstone is thrown up in vertical beds striking nearly 

 east and west, and is in a state approaching to quartz rock, being much indurated and 

 in parts cellular, the cells frequently containing green earth and malachite 5 whilst on the 

 absolute face and summit of the trap of Little Caradoc, as well as on the eastern face of 

 the Lawley, the sandstone is only to be detected in the state of true quartz rock, in 

 most instances the trace of bedding being entirely destroyed, and the rock resting as 

 a thin cover or in detached fragments upon the trap. Similar masses of quartz rock 

 adhere to the sides of these trap hills at the Battle Stones. 



In one of the quartzose veins, proceeding from the Caer Caradoc, the Rev. J. Yates 

 discovered crystallized galena, an interesting fact as connected with the theory of me- 

 tallic veins, respecting which much additional information will be communicated in the 

 twenty-second chapter, upon the volcanized mining tracts west of the Stiper Stones. 

 The environs of the Caradoc alone would, however, be almost sufficient to lead us to be- 

 lieve that veins have frequently been filled or enriched with metallic substances during 

 the evolution of igneous matter through sedimentary deposits, for the altered sandstones 

 around the edges of the protruding masses of trap near Hope Bowdler, are traversed to 

 some extent by veins of copper ore, some of which have been slightly worked at former 

 periods 1 . 



Without quitting the county of Salop, and restricting our observations to the vicinity 

 of the Wrekin and the Caradoc, we are thus furnished with numerous examples of 

 great mineral changes which have taken place in these sandstones, when they are in 

 contact with, or in the proximity of certain rocks of intrusive characters and igneous 

 origin, and the inference appears to be irresistible, that the sandstone has undergone the 

 change of composition through the action of heat, evolved during the eruption of the 

 volcanic matter. 



1 Mr. Yates noticed vertical strata of quartz rock passing into sandstone with a vein of trap passing through 

 them. He also observed malachite in the quartz rock and in those peculiar sandstones which I have termed vol- 

 canic grit, and also in the ordinary sandstones of Long Lane quarry. Geol. Trans, vol. 2, p. 246. This mineral 

 (green carbonate of copper) is largely disseminated in the adjoining districts to the westward. (See chapter 22.) 



