204 



INTRUSIVE IGNEOUS ROCKS. 



gYlS. ll0rnblende crystals irregularly scattered through a white 



— or brownish felspathic base. 



"W all-case 4. 77 ,-» -%*+***' 



Jbrom the same mass as ISo. 136. 



144— Greenstone — Pen-ar-fynydd, 3 miles east of Aber- 

 daron, Caernarvonshire, Large plates or scales of horn- 

 blende, with a very few small felspar crystals. 

 . From the same mass as Nos. 136 and 143. 



145.— Greenstone. — Llyn Cwm-y-ffynon, near the top 



Map 75, 



of the Pass of Llanberis, Caernarvonshire. 



N.E. Light green hornblende and white felspar crystals! 



Largely crystalline in structure. 



From an intrusive line of greenstone about a mile in 



length. 



into hone-stone. 



Alters the slaty rocks with which it is in contact 



146.— Greenstone.— Pont-y-Gromlech, Llanberis, Caer- 

 narvonshire. Map 75, N.E. Similar to the last. 



From a mass of greenstone which pierces the felspathic 

 trap, Nos. 100 and 101, (Section No. a, above,) that under- 

 lies the calcareous ashes of Snowdon. 



1 47. — Greenstone. 



Bettws-y-Coed, Caernarvonshire. 



Llyn-Pen-Craig, U mile north of 



Map 78, S.E. Con- 



sists of felspar and hornblende in distinctly crystallized 

 fragments with slender crystals of felspar often traversing 

 both of the other minerals. Felspar predominates. 



From a line of greenstone injected between beds of 

 slate and felspathic ashes, equivalents of the calcareous 

 ashes that form the summit of SnoWdon. 



Merionethsl 



shire chiefly run in lines, which, in many cases, have been 

 injected between the beds, or nearly so, as shown in the 

 sections at the top of the case. At first sight on the ground, 

 they might often be supposed to be truly interbedded rocks, 

 like the felspathic lavas of the same district, but their nature 

 is easily distinguished by the circumstance that the rocks 



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