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RADNORSHIRE, NEAR BUILTH. 



207 



ones, from which the calc spar has been decomposed, are 

 lined with brown iron ore. 



From an intrusive branching mass, about 



length. 



14 mile in 



The porcelainic alteration it produces on the Llan- 

 deilo flags is well seen on the banks of the river Wye, north- 

 west of Builth. The unaltered Upper Silurian rocks of the 



May 



Pentame 



The same 



i 



is the case in the quarry behind Wellfield House. These 

 Pentamerus beds here lie highly unconformably in the Llan- 



;. For Pentamerus oblongus see 66, Case No. 41. 



159. — Greenstone. — Garth, north end of the Carneddau, 

 Radnorshire, near Builth, Brecon. Map 66, S.W. Crys- 

 talline mixture of felspar and light and dark green horn- 

 blende. Felspar predominates. 



From a mass 3 miles in length between Llanelwedd and 

 the north end of the Carneddau. It is intruded among the 

 slates and felspathic ashes of the Llandeilo flags, but prin- 

 cipally overlies them. See section above, No. 6, rocks 

 Nos. 159 to 163. 



160. — Vesicular felspathic trap. — The Rocks, Llan- 



degley, Radnorshire. Map 56, S.E. Yellowish -grey fel- 

 spathic rock, filled with felspar crystals decomposing of a 

 dark brown colour. 



From an intrusive mass forming a bold hill called the 

 Rocks. It seems like a bed of lava, having been intruded 

 between the beds of slate, which have been altered by it both 

 on its under and upper surface. Were it a true bed the 

 rocks in contact with its upper surface would remain un- 

 altered. 



161. 



Greenstone Craig Q 



Radnorshire. 



patches of white felspar 

 crystals. 



Light green granular felspathic rock, with 



small hornblende 



and 



a few 



From the north end of the same rocks as No. 160, near 

 which they are overlaid by unaltered Wenlock shale, quar- 

 ried for building stone. 



TJPPEB 



Gallebt. 

 Wall-case 4. 



