424 THE LEAD OF ALSTON MOOR. 



between Wensleydale on the south and Teesdale on the north ; 

 the lodes all run east and west, though in the south-east of the 

 district there are a few lodes which run from north-east to south- 

 west. South of the Swale, the ore frequently lies in caverns in the 

 limestone rather than in true lodes. 



The lead veins in Alston Moor occur in fissures, where the strata 

 are sometimes dislocated 200 feet. On the downthrow side of the 

 fault the limestone is compact with scarcely a parting ; on the up- 

 throw side, the limestone is broken up with joints, often filled with 

 clay. The joints are most numerous near to the surface ; most 

 numerous in limestones, and least numerous in shales. The veins are 

 grouped by Mr. Wallace into three kinds. The first run between 

 K 60 E. and S. 60 E. The second class includes the veins running 

 north and south. Both these classes of veins are intersected by 

 small veins, some of which run S. 55 E. and others S. 55 W. 

 magnetic. These veins contain lead above, and lead and copper 

 below. The great sulphur vein, as it is termed, is not less than 300 

 feet wide at Crossgill. It is filled with quartz and iron pyrites, and 

 has the aspect of being formed by a great number of parallel fissures. 

 It runs from N. W. to S.E. At Cashburn it consists of quartz, and 

 forms low round hills ; it is supposed to be posterior in date to the 

 cross veins of Alston Moor. It is parallel to a whin dyke. Among 

 the east-and-west veins are the Browngill and Benty Field veins. The 

 Benty Field ramifies into weak strings, but at Dryburn the strings 

 unite and form a wide vein, which dislocates the strata 60 feet; 

 and this is the character of many of the veins of this district, though 

 the throw is usually much less. Xext to the Browngill, Fletcheras 

 vein is the strongest in this district. The cross veins are of all 

 magnitudes the Carrs vein has a dislocation of 260 feet, but the 

 throw varies with the vein and is sometimes only a few inches. The 

 contents of the cross veins are generally softer and less compact than 

 those of the E. and W. veins. It is held by Mr. Wallace that the 

 cross veins were either anterior to or contemporary with the veins 

 that run E. and W. 



Lead ore is found mixed with quartz, carbonate and sulphate of 

 lime, carbonate and sulphide of iron, fluor spar, baryta, &c. The 

 richest deposits are in the upper part of the mountain limestone ; 

 but in the lower part of the mountain limestone, which is traversed 

 by augite andesites, there is very little lead ore. The deposits of 

 lead ore in the veins are generally divided from each other in this 

 district by shale. The Kampgill vein is uniformly wide, and well 

 filled with vein minerals. 1 



The mining district of Derbyshire lies between Buxton and 

 Castleton on the north, and Cromford and Wirksworth on the south. 

 It is about thirty miles long by twelve miles broad, and is most 

 productive on the eastern side. In this district the richest deposits 

 occur when the strata form synclinal folds. 



1 Wallace on Lead Deposits of Alston Moor. 



