188 



MINERALS OF THE OLD RED SANDSTONE. 



of Brecon, Monmouth, and Hereford, is probably due to large tracts of this region not 

 having been the theatre of those violent disturbances which have affected the Lower 

 Silurian Rocks and the coal measures. 



Minerals in the Old Red Sandstone. 



The Old Red Sandstone does not contain any mineral veins worthy of notice. Even 

 the ores of iron, which are more or less abundant in formations of every age, from the 

 newest tertiary down to the carboniferous deposits included, never occur in distinct 

 masses, though iron is the chief colouring matter, as well as cementing ingredient of all 

 the rocks in the Old Red System. 



This poverty in metallic veins is of great interest, when connected with the almost 

 total absence of igneous or intrusive rocks, as just explained ; for it will be shown else- 

 where, that in those districts which abound with trap, both altered rocks, and metallic 

 veins, are of common occurrence 1 . 



Throughout the whole of the great territory occupied by this System, I have met 

 with only two examples of metalliferous veins, which have been deemed worthy of the 

 slightest attention, and these are both of copper ore. One occurs at Hayton's-bent, in 

 the escarpment of the cornstone Hills north of Ludlow, the other in Brecknockshire. 



In the first case the works, which never produced any profits, have been abandoned for one hundred 

 years ; and as there are no records, the only information to be derived, is from the appearances at 

 the mouths of the old trial shafts or galleries. From these we may infer, that the vein ran from 

 N.E. to S.W., or nearly parallel to the strike of the beds, which are inclined very slightly to the 

 S.E. Out of the refuse stuff, I collected several small specimens of green carbonate and grey 

 copper, in a matrix of calcareous spar running in small veins through fragments of sandstone. The 

 Brecon example is at Felin Fach, four miles north-east of the town of Brecon, and on the right bank 

 of a mountain stream which descends from the Mynidd Llandefelle. The strata here, though con- 

 taining no cornstone as in Shropshire, belong to the lower part of the same group, and consist of 

 hard chocolate- and greenish-coloured sandstones, with a granular quartzose rock, the base of which 

 is interspersed with bright pink grains of quartz, and a few blotches of green earth. Other bands 

 of greenish grit have their surfaces speckled with brown, these differences of colour being probably 

 dependent on the mutual presence of the silicate or the oxide of iron. The vein stuff thrown out 

 from the trial shafts, (the works having been abandoned,) contains much crystallized carbonate of 

 lime, chiefly of the primary rhomb, with sulphurets of copper and iron partially diffused through a 

 mass, the remainder of which is made up of scales of green earth, crystallized blende (black jack of 

 the miners), in very minute particles, and a little red oxide of iron. 



Judging from these examples of slender and poor veins, and their entire absence in 



1 See particularly the chapter on the Shelve and Cornden tract, following the description of the Silurian 

 Rocks in Shropshire. 



