* 



" 



•-\ 



% 





GREENSTONE DYKES, LLYN PADARN, LLANBERIS 213 



Form when removed from igneous intrusive masses. It is 

 placed in this collection to show the extreme amount of 

 alteration which the rocks numbered 186 to 191 have 

 undergone. 



Upper 

 Galleet. 



Wall-case 4. 





i 







.s 







tt 1 





t ft 











lli 



I . 



. 







p^ 





■ 



Id' 



: 



■> 





: 



i 



i 







j 



f 





Greenstone dykes, piercing intrusive and igneous rocks, 

 of Llyn Padarn, and the Cambrian slates and 



above it. 



grits 



193.— Greenstone.— Llyn Padarn, south-west side, near 



Dark green finely crys- 



Llanbe 



Caernarvonshire. 



tallized, hornblende and felspar mass, with interspersed 

 radiated masses of epidote. It pierces No. 185. 



194 



Greenstone — South-west side of Llyn Padarn, 

 Llanberis. Dark green rock ; felspar and hornblende finely 

 crystallized, with large interspersed patches of felspar. It 

 pierces No. 175. 



195. — Greenstone.— South-west side of Llyn Padarn, 



near Llanberis. 



blende crystals 



It pierces No. 185. 



Light green felspathic base, with horn- 



(asbestos*). 



196.— Greenstone.— South-west side of Llyn Padarn, 

 Llanberis, Caernarvonshire. Fine grained dark green rock 



spar. It pierces No. 185. 



felspa 



197. — Greenstone North 



side of Llyn Padarn 



below slate quarries, Llanberis. Compact dark green rock 

 with large stripes of epidote and quartz. 



These dykes, No. 193 to No. 197, run in narrow lines, 

 indiscriminately piercing the quartz porphyries and Cam- 

 brian and Silurian rocks of Llanberis. They are, however, 

 probably of much later date than the large intrusive masses 

 and the Lower Silurian traps and ashes ; and containing oc- 

 casionally cleaved fragments of slate (at Penrhyn quarries), 



they would appear to have been intruded after those mecha 



f 



