110 



ALTERED SILURIAN ROCKS. 





gS. Pen-y-gwryd, alters the slate with which it ia in contact 

 Wali^e45. mt ° honestone ' Ma P 75 N.E. Merionethshire. 



68.— Llandeilo flags, altered fossilliferous pyritotu 

 black slate. In immediate proximity to qreenstone f "NTn 



158, 163, and 164, Case t).-Banks of the Wye, RadZr 

 shire, near Builth. 



68a—LLANDEiLO flags, Carneddau, Radnorshire nenr 



Builth. Porcelainised 



69. — Ditto, as above. 

 70. 



Pant-Pi 



3 miles south-east of Chirbury. Altered by neighbouring 



greenstone. See 151, Case 



71. 

 brokeshire. 



Map 



Llandeilo flags, near Llanivnda, Fishguard, P em - 



Banded fine siliceous rock, partly porcelainised 



if 



Head. Map 40. 



72. — Ditto, more weathered. 



73. — Ditto, still more porcelainised. 

 74 — Ditto, more completely metamorphosed. The silica 

 having begun to crystallize in nests. 



75 — Slaty Silurian rock, porcelainised. In the neigh 

 bourhood of granites, &c 

 glesea. Map 78 N.W. 



•Altered slate, a species of imperfect gritty snake- 



Mona 



Mine, 



76. 



don greenstone, Montgo 

 No. 153, Case ^. nacre \ 



itrusion of the Corn- 



Map 60 S.E. See 



Q 



77— Altered slate, snakestone, Forth Treuddyn 



Merionethshire 



75 



Altered by intrusive greenstone. 



«. 1 ' 7 f' 1 ~ TAL ^° SE schist ' with iron Pyrites, traversed by 

 *~ia i„^__ ™ -Symdde, 6 miles north of Dolgelli, Me- 



75 S.E. Probably metamorphic, the alte- 



Map 



stone. 



of masses of g 



79 — Talcose schist, as above 



Diffvvys 



quartz 



Quarry, Ffestiniog, Merionethshire 



) 



This rock passes into felspathic ash. 





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