







:■ 



ffl,-fc 



SYENITE. — GREENSTONE. 



243 



152. — Syenite, chiefly 



fi 



hornblende and a small proportion of quartz. — Strontiar., 



Argyleshire. 

 153. — Grey syenite, or, syenitic porphyry, composed 



of prismatic crystals of hornblende, with white felspar and 

 quartz, and a few specks of iron pyrites. — Used as a building 



stone. — Guernsey. 



154. — Fine-grained, reddish-grey granitic rock, con- 

 taining imperfect crystals of a lighter coloured felspar. 



This rock forms part of a granitic dyke which extends 

 from the western end of Penvivian Hill towards Belovely 

 Beacon. See Map 30. — Great Brin, near Roche, Cornwall. 



155. — Porpiiyritic greenstone, chiefly composed of pris- 



f< 



a little trans- 



lucent quartz, and a few occasional spangles of mica. — Pen- 

 ar-fynydd, 3 miles east of Aberdaron, Caernarvonshire. 



Upper 

 Gallery. 



Wall-cases 

 6 and 7. 





- 







i 





I if- 



9 





t 



<j 



ff 



; 



f 



Greenstone, Hornblende rock, Toadstone, Amygda- 

 loid, &c. 



156 to 158. — Greenstone (variety — hyper sthene rock) 



d/ 



Hanter Hill is a pic- 



turesque mass of rock, rising to a height of 1,250 feet above 

 the sea level, and altering and contorting the upper Silurian 

 strata, amongst which it is injected along a great line of dis- 

 location. It forms an extension of the same range of erup- 

 tive Trap as the S tanner Rocks, No. 178. Map 56, S.E., 

 and Horizontal Sections, Sheet No. 27. — Hanter Hill, King- 

 ton, Herefordshire. 



159. — Fine-grained greenstone composed of brownish 



felsp 



md hornblende, in nearly equal proportions. — Sea 

 coast A\ miles south of Clynnog Fawr, West of Yr Eifl, 



greenstone, forming some re- 



Caernarvonshire, 



1 60. — Large-grained 

 markable rocky tors near the cliffs. It might be usefully 



employed for roads and in massive structures. — Tintagel, 

 Cornwall. 



