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GREENSTONE. 



245 



171.— -Porpiiyritic greenstone; composed of crystals of 

 white felspar in a felspatho-hornblendic base. — Bwlch Mawr, 

 1^ miles south-east of Clynnog Fawr, Caernarvonshire. 



Porpiiyritic greenstone in a decomposing state, 



Upper 



Gallery. 



Wall-cases. 

 and 7, 



172 



composed of crystals of white felspar in a hornblende base. 



Dun, Coast of Ayrshire, Scotland. 



173. — Felspathic greenstone, composed of felspar 

 and hornblende in nearly equal quantities. Furnishes a 

 good building stone. — Careg-y-rimbill ("Gimblet Rock"), 

 Pwllheli, Caernarvonshire. 



r 



174. — Greenstone, composed of felspar and augite in 

 nearly equal proportions. — Salisbury Crags, Edinburgh. 

 175. — Felspathic greenstone, containing crystals of 



iron pyrites. (Part of a dyke.) This and some other trap- 

 pean rocks of the neighbourhood might be usefully employed 

 on the roads of the vicinity, which are too frequently mended 

 with quartz. — West Pentire, Crantock, Cornwall. 



176. — Small-grained greenstone, composed of an inti- 



mate mixture of felspar and hornblende (?), and weathering 



Scot- 



gmous brown. — Campsie Hills, 



Stirlingshir 



e 



ferru 

 land. 



177 — Concretionary greenstone, weathering into fer- 

 ruginous-brown concentric concretions (from Coal Mea- 



sures). — 2 miles south of Atherstone, Warwickshire. 



178. 



felsp 



with small specks of black mica, often steatitic on surfaces. 



An eruptive rock intruded among 



and altering 



dlow) 



Upper 



Map 56, S.E.— Stanner Rocks, 



near Kington, Herefordshire. 



Compact greenstone, from a dyke 



179. 



Cambrian Rocks. 

 Dublin. 



traversing 



Baily Lighthouse, Howth, County 



180. — Compact greenstone. — Between Lay Point and 

 St. Ives, Cornwall. 



181.— Greenstone. (See "Report on Cornwall," p. 82.) 

 St. Mewan, Cornwall. 



182— Greenstone. — Trenoweth. Cuiy, Cornwall. 



